DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Response to Amendment
This Office Action is in response to the amendments filed on 04/10/2026.
Applicant’s amendments filed 04/10/2026 have been fully considered and reviewed by the examiner. The examiner notes the amendment of claims 1-2, 4, 6-7, 12-13, and 18.
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claims 1-22 are rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention
Claim 1 recites limitations “can be applied (line 8)”. The phrase “can” renders the claim indefinite because it is unclear whether the limitation(s) following the phrase are part of the claimed invention.
Claim 1 recites limitations “the bulk of the device” (line 9) that lacks antecedent basis in the claim.
Claim 18 recites limitations “a bias can be applied (line 11)”. The phrase “can” renders the claim indefinite because it is unclear whether the limitation(s) following the phrase are part of the claimed invention.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 1-4, 6-16, and 17 are rejected under 35 U.S.C. 103 as being unpatentable over US 2018/0047840 to Nakamura et al. (hereinafter Nakamura) in view of Chen et al. (CN 108417662 A, hereinafter Chen), Chen et al. (US 2018/0166565, hereinafter Chen’565), Kim et al. (US 2004/0046176, hereinafter Kim), Lin et al. (US 2018/0047822, hereinafter Lin), and Wu et al. (US Patent NO. 6,586,781, hereinafter Wu) (the reference “Review of using gallium nitride for ionizing radiation detection” by Wang et al., (2015) Appl. Phys. Rev. 2, 031102, cited in IDS, hereinafter Wang, is presented as evidence).
With respect to claim 1, Nakamura discloses a semiconductor high electron mobility transistor (HEMT)-based device (Nakamura, Fig. 2, ¶0036-¶0043, ¶0046-¶0059), wherein the device comprises:
a substrate (10) (Nakamura, Fig. 2, ¶0036-¶0037, ¶0041);
a nucleation layer (e.g., AlN) (Nakamura, Fig. 2, ¶0036-¶0037, ¶0046-¶0054) formed on the substrate (10); a gallium nitride (GaN) buffer layer (11) arranged on the nucleation layer; a GaN channel layer (21) arranged on the GaN buffer layer (11); an aluminum nitride (AIN) spacer layer (22) arranged on the GaN channel layer (21);
a barrier layer (23) (Nakamura, Fig. 2, ¶0036-¶0037, ¶0051) arranged on the AIN spacer layer (22);
a GaN cap layer (25) (Nakamura, Fig. 2, ¶0036-¶0037, ¶0054) arranged on the barrier layer (23);
a source (32) (Nakamura, Fig. 2, ¶0036, ¶0058), a drain (33) and a gate (31) (Nakamura, Fig. 2, ¶0036, ¶0059), wherein the source (32) and the drain (33) are formed on the GaN cap layer (25) with alloying (e.g., a metal multilayered film of Ta/Al on the underlying nitride layers is heat-treated to establish ohmic contacts) to form ohmic contacts to an underlying GaN channel layer (21), and the gate (31, a metal film Ni/Au is formed without heat-treated process after forming ohmic contacts) is formed on the GaN cap layer (25) without metallurgical alloying to render a Schottky junction (Nakamura, Fig. 2, ¶0059).
Further, Nakamura does not specifically disclose (1) a semiconductor HEMT-based device configured to detect ionizing radiation; a backside terminal to which a bias can be applied to enhance collection of charges generated in the bulk of the device by directing them vertically towards the GaN channel layer; and a multiplication region at the gate, wherein charge carriers generated by the radiation in underlying GaN layers are collected in the GaN channel layer and amplified by impact ionization by a high electric field at a gate edge facing a drain contact; (2) an electrically insulating silicon nitride (SiNx) passivation layer arranged on the GaN cap layer, wherein vias are fabricated through the SiNx passivation layer to allow connection of metal terminals of each of the source, drain and gate to a GaN semiconductor surface.
Regarding (1), Chen teaches forming Gallium Nitride-based Radial detector (Chen, Abstract, Fig. 1, pp. 1-4) comprising high electron mobility transistor (HEMT) for radiation detection, cosmic ray detection, high energy accelerated particle collision product detection, nuclear fission/fusion to radiation detection. The GaN-based HEMT radial detector has signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio. In the GaN-based HEMT radial detector, the radiation (112) (Chen, Abstract, Fig. 1, p. 3) is absorbed in the GaN buffer layer (103) underlying the GaN channel layer (104) and is converted into electric signal that is amplified by self-signal amplifying function of GaN detector, and transmitted to high electron transport efficiency transistor output, such that the charge carriers generated by the radiation (112) in the underlying GaN layers (103) are collected in the GaN channel layer (104) and multiplied. In Chen, the back electrode (101) is formed under the amplification region (103) to provide bias to the amplification region (103) to facilitate absorbing the radiation (112) to generate electron-hole pairs (Chen, Fig. 1, pp. 3-4).
Further, Chen’565 teaches that when the HEMT transistor structure (Chen’565, Fig. 1L, ¶0003, ¶0015-¶0039) is operated in high power devices, a high electric field occurs at the gate-to-drain region (Chen’565, Fig. 1L, ¶0039), and the gate operation voltage of the HEMT device is controlled to provide desired performance of the HEMT transistor.
Further, Kim teaches forming avalanche phototransistor (Kim, Fig. 1, ¶0003, ¶0025-¶0032, ¶0059), wherein the electrons created in the photo-absorption layer are multiplicated by impact ionization occurred in the multiplication layer due to a very high electric field effect, and the avalanche gain by the impact ionization effect is obtained (Kim, Fig. 1, ¶0059).
Thus, a person of ordinary skill in the art would recognize that a high electric field occurred at the gate-to-drain region of the HEMT transistor as taught by Chen’565, wherein the HEMT transistor is configured for radiation detection as taught by Chen, would result in multiplication of electrons by impact ionization due to a very high electric field effect as taught by Kim, to provide high performance photo-transistor.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the HEMT transistor of Nakamura by forming GaN-based HEMT radial detector as taught by Chen, and controlling the gate operation voltage of the HEMT device to control a high electric field occurred at the gate-to-drain region as taught by Chen’565, wherein the electrons created in the photo-absorption layer of Nakamura/Chen/ Chen’565 are multiplied by impact ionization due to a very high electric field effect as taught by Kim to have a semiconductor HEMT-based device configured to detect ionizing radiation; a backside terminal to which a bias can be applied to enhance collection of charges generated in the bulk of the device by directing them vertically towards the GaN channel layer; and a multiplication region at the gate, wherein charge carriers generated by the radiation in underlying GaN layers are collected in the GaN channel layer and amplified by impact ionization by a high electric field at a gate edge facing a drain contact, in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio; to control operation of the HEMT-based device having high mobility; and to provide high performance photo-transistor (Chen, Abstract, pp. 1-3; Chen’565, ¶0003, ¶0015, ¶0039; Kim, ¶0008-¶0009, ¶0059).
Further, the recitations of claim 1 "a bias can be applied to enhance collection of charges generated in the bulk of the device by directing them vertically towards the GaN channel layer" are intended-use recitations. Note that a recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim. See, e.g., In re Pearson, 181 USPQ 641 (CCPA); In re Minks, 169 USPQ 120 (Bd Appeals); In re Casey, 152 USPQ 235 (CCPA 1967); In re Otto, 136 USPQ 458, 459 (CCPA 1963). See MPEP §2114.
Regarding (2), Lin teaches forming a HEMT transistor (Lin, Fig. 7B, ¶0002, ¶0033-¶0046 comprising an active layer (120) (Lin, Fig. 7B, ¶0034) including a channel layer (122) and the barrier layer (124) and a passivation layer (140/180) (Lin, Fig. 7B, ¶0036-¶0039) comprising silicon nitride on the active layer (120) to prevent a current leakage, wherein vias (192/194/196) are fabricated through the silicon nitride passivation layer (140/180) to allow connection of metal terminals of each of the source (150), drain (160) and gate (130) to a semiconductor surface of the active layer (120).
Further, Wu teaches forming GaN-based HEMT device (Wu, Fig. 2, Col. 2, lines 39-45; Col. 4, lines 44-67; Col. 5, lines 1-28) having improved amplification characteristics and comprising a passivation layer (44) including silicon nitride (SixNy) having a high percentage of silicon to prevent the capture of barrier layer electrons during operation, and thus to improve the device performance characteristics.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the HEMT transistor of Nakamura by forming a passivation layer as taught by Lin , wherein on the passivation layer is formed on the active layer of Nakamura including a GaN cap layer, and comprised of specific percentage of silicon as taught by Wu to have an electrically insulating silicon nitride (SiNx) passivation layer arranged on the GaN cap layer, wherein vias are fabricated through the SiNx passivation layer to allow connection of metal terminals of each of the source, drain and gate to a GaN semiconductor surface, in order to prevent a current leakage; and to prevent the capture of barrier layer electrons during operation, and thus to improve the device performance characteristics (Lin, ¶0002-¶0003, ¶0038-¶0039; Wu, Col. 1, lines 15-17; Col. 2, lines 39-45; Col. 4, lines 64-67; Col. 5, lines 1-28).
Regarding claims 2-3, 6, 8-10, 13, and 14, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura does not specifically disclose the HEMT-based device, wherein the multiplication region at the gate is adapted to achieve an acceptable signal to noise ratio (SNR) (as claimed in claim 2); wherein the multiplication region is produced via voltage biasing, and adapted to achieve acceptable signal to noise ratio (SNR) (as claimed in claim 3); wherein, when the device is in operation, a bias is applied to the backside terminal to enhance collection of charges generated in a bulk by directing them vertically towards the GaN channel layer (as claimed in claim 6); wherein the ionizing radiation comprises beta-particles (as claimed in claim 8); wherein the ionizing radiation comprises alpha-particles (as claimed in claim 9); wherein the ionizing radiation is produced within the HEMT-based device or substrate (as claimed in claim 10); wherein, when the device is in operation, gate-edge amplification of carriers is used to detect ionizing particles (as claimed in claim 13); wherein, the ionizing radiation is minimum ionizing particles (as claimed in claim 14).
Further, the recitations of claims 6 (“when the device is in operation, a bias is applied to the backside terminal to enhance collection of charges generated in a bulk by directing them vertically towards the GaN channel layer”) and 13 ("when the device is in operation, gate-edge amplification of carriers is used to detect ionizing particles") are intended-use recitations. Note that a recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim. See, e.g., In re Pearson, 181 USPQ 641 (CCPA); In re Minks, 169 USPQ 120 (Bd Appeals); In re Casey, 152 USPQ 235 (CCPA 1967); In re Otto, 136 USPQ 458, 459 (CCPA 1963). See MPEP §2114.
However, Nakamura discloses forming a HEMT device comprising a cap layer (25) (Nakamura, Fig. 2, ¶0036-¶0037, ¶0054, ¶0062-¶0063) to prevent the current collapse phenomenon during operation of the device, wherein a drain voltage (Vds) and a varying gate voltage (Vgs) pulse are applied to the drain and the gate, respectively.
Further, Chen teaches forming Gallium Nitride-based Radial detector (Chen, Abstract, Fig. 1, pp. 1-4) comprising high electron mobility transistor (HEMT) for radiation detection, cosmic ray detection, high energy accelerated particle collision product detection, nuclear fission/fusion to radiation detection. In the GaN-based HEMT radial detector of Chen, the radiation (112) (Chen, Abstract, Fig. 1, p. 3) is absorbed in the GaN buffer layer (103) underlying the GaN channel layer (104) and is converted into electric signal that is amplified by self-signal amplifying function of GaN detector, and transmitted to high electron transport efficiency transistor output, such that the charge carriers generated by the radiation (112) in the underlying GaN layers (103) are collected in the GaN channel layer (104) and multiplied. The GaN buffer layer (103) underlying the GaN channel layer (104) is a designated multiplication region to provide the GaN-based HEMT radial detector having high signal-to-noise ratio (Chen, Fig. 1, pp. 2-3). In Chen, the back electrode (101) is formed under the amplification region (103) to provide bias to the amplification region (103) to facilitate absorbing the radiation (112) to generate electron-hole pairs (Chen, Fig. 1, pp. 3-4).
Further, it is known in the art (e.g., as evidenced by Wang, Abstract, pp. 031102-1 to 1031102-6) that GaN as a wide band-gap semiconductor material having properties such as large displacement energy and high thermal stability is used to detect alpha particles, X-rays, and for beta particles response.
Further, Chen’565 teaches that a high electric field occurs at the gate-to-drain region (Chen’565, Fig. 1L, ¶0039) of the HEMT-based transistor.
Further, Kim teaches forming avalanche phototransistor (Kim, Fig. 1, ¶0003, ¶0025-¶0032, ¶0059), wherein the electrons created in the photo-absorption layer are multiplicated by impact ionization occurred in the multiplication layer due to a very high electric field effect, and the avalanche gain by the impact ionization effect is obtained (Kim, Fig. 1, ¶0059).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the HEMT transistor of Nakamura/Chen/Chen’565/Kim/ Lin/Wu by forming GaN-based HEMT radial detector comprising amplification function by using the GaN layer under the GaN channel layer as taught by Chen, wherein the electrons created in the photo-absorption layer of Nakamura/Chen/ Chen’565 are multiplied by impact ionization due to a very high electric field effect as taught by Kim to have the HEMT-based device, wherein the multiplication region at the gate is adapted to achieve an acceptable signal to noise ratio (SNR) (as claimed in claim 2); wherein the multiplication region is produced via voltage biasing, and adapted to achieve acceptable signal to noise ratio (SNR) (as claimed in claim 3); wherein, when the device is in operation, a bias is applied to the backside terminal to enhance collection of charges generated in a bulk by directing them vertically towards the GaN channel layer (as claimed in claim 6); wherein the ionizing radiation comprises beta-particles (as claimed in claim 8); wherein the ionizing radiation comprises alpha-particles (as claimed in claim 9); wherein the ionizing radiation is produced within the HEMT-based device or substrate (as claimed in claim 10); wherein, when the device is in operation, gate-edge amplification of carriers is used to detect ionizing particles (as claimed in claim 13); wherein, the ionizing radiation is minimum ionizing particles (as claimed in claim 14), in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio; to control operation of the HEMT-based device having high mobility; and to provide high performance photo-transistor (Chen, Abstract, pp. 1-3; Chen’565, ¶0003, ¶0015, ¶0039; Kim, ¶0008-¶0009, ¶0059).
Regarding claims 4 and 7, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura does not specifically disclose he HEMT-based device, wherein, when the device is in operation, a voltage bias is applied to the drain to enhance sensitivity of the HEMT-based device (as claimed in claim 4); wherein, when the device is in operation, a varying voltage is applied to the gate to enhance sensitivity of the HEMT-based device (as claimed in claim 7).
Further, the recitations of claims 4 (“when the device is in operation, a voltage bias is applied to the drain to enhance sensitivity of the HEMT-based device”) and 7 ("when the device is in operation, a varying voltage is applied to the gate to enhance sensitivity of the HEMT-based device ") are intended-use recitations. Note that a recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim. See, e.g., In re Pearson, 181 USPQ 641 (CCPA); In re Minks, 169 USPQ 120 (Bd Appeals); In re Casey, 152 USPQ 235 (CCPA 1967); In re Otto, 136 USPQ 458, 459 (CCPA 1963). See MPEP §2114.
However, Nakamura teaches forming a HEMT device comprising a cap layer (25) (Nakamura, Fig. 2, ¶0036-¶0037, ¶0054, ¶0062-¶0063) to prevent the current collapse phenomenon during operation of the device, wherein a drain voltage (Vds) and a varying gate voltage (Vgs) pulse are applied to the drain and the gate, respectively.
Further, Chen teaches forming Gallium Nitride-based Radial detector (Chen, Abstract, Fig. 1, pp. 1-4) comprising high electron mobility transistor (HEMT), wherein the radiation (112) (Chen, Abstract, Fig. 1, p. 3) is absorbed in the GaN buffer layer (103) underlying the GaN channel layer (104) and is converted into electric signal that is amplified by self-signal amplifying function of GaN detector, and transmitted to high electron transport efficiency transistor output.
Further, Chen’565 teaches that a high electric field occurs at the gate-to-drain region (Chen’565, Fig. 1L, ¶0039) of the HEMT-based transistor, and the gate operation voltage of the HEMT device is controlled to provide desired performance of the HEMT device.
Thus, a person of ordinary skill in the art would recognize that releasing the electrons trapped in the GaN layers and the barrier would enhance the sensitivity of the Gallium Nitride-based Radial detector including HEMT device of Nakamura/Chen/Chen’565/Kim/Lin/Wu.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the HEMT-based device of Nakamura/Chen/Chen’565/Kim/
Lin/Wu by forming GaN-based HEMT radial detector comprising amplification function by using the GaN layer under the GaN channel layer as taught by Chen, wherein the gate operation voltage of the HEMT device is controlled as taught by Chen’565 to have the HEMT-based device, wherein, when the device is in operation, a voltage bias is applied to the drain to enhance sensitivity of the HEMT-based device (as claimed in claim 4); wherein, when the device is in operation, a varying voltage is applied to the gate to enhance sensitivity of the HEMT-based device (as claimed in claim 7), in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio; and to efficiently prevent current collapse, and to provide desired performance of the HEMT device (Chen, Abstract, pp. 1-3; Nakamura, ¶0062-¶0064; Chen’565, ¶0039).
Regarding claim 11, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura does not specifically disclose the HEMT-based device, configured to detect a transient behavior of high energy particles transferring energy into a semiconductor material.
Note that the limitations “configured to detect the transient behavior of the high energy particles transferring energy into the semiconductor material” are interpreted as functional language limitations. While features of an apparatus may be recited either structurally or functionally, claims directed to an apparatus must be distinguished from the prior art in terms of structure rather than function. In re Schreiber, 128 F.3d 1473, 1477-78, 44 USPQ2d 1429, 1431-32 (Fed. Cir. 1997).
In the instant case, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device having the HEMT structure to detect the radiation in the GaN layer underlying the GaN channel layer (in view of Chen).
Further, it is known in the art (e.g., as evidenced by Wang, Abstract, pp. 031102-1 to 1031102-6) that GaN as a wide band-gap semiconductor material having properties such as large displacement energy and high thermal stability is used to detect alpha particles, X-rays, and for beta particles response.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the HEMT-based device of Nakamura/Chen/Chen’565/Kim/ Lin/Wu by forming the GaN buffer layer underlying the channel layer and appropriately biasing the gate and the drain to have the HEMT-based device, configured to detect a transient behavior of high energy particles transferring energy into a semiconductor material, in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio (Chen, Abstract, pp. 1-4).
Regarding claim 12, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura does not specifically disclose the HEMT-based device, wherein, when the device is in operation, the charge carriers generated by the ionizing radiation passing between the gate and the drain follow a substantially linear path.
Further, the recitations of claim 12 “when the device is in operation, the charge carriers generated by the ionizing radiation passing between the gate and the drain follow a substantially linear path" are intended-use recitations. Note that a recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim. See, e.g., In re Pearson, 181 USPQ 641 (CCPA); In re Minks, 169 USPQ 120 (Bd Appeals); In re Casey, 152 USPQ 235 (CCPA 1967); In re Otto, 136 USPQ 458, 459 (CCPA 1963). See MPEP §2114.
In the instant case, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device having the HEMT structure comprising the gate and the drain, wherein the operational characteristics of the HEMT device depends on the structure of the HEMT-based device and the voltage applied to the gate and the drain.
Further, Chen teaches the Gallium Nitride-based Radial detector (Chen, Abstract, Fig. 1, pp. 1-4) comprising high electron mobility transistor (HEMT), wherein the radiation (112) (Chen, Abstract, Fig. 1, p. 3) is absorbed in the GaN buffer layer (103) underlying the GaN channel layer (104) and is converted into electric signal that is amplified by self-signal amplifying function of GaN detector, and transmitted to high electron transport efficiency transistor output.
Since all structural limitations of claim 1 and claim 12 are discloses by the combination Nakamura/Chen/Chen’565/Kim/Lin/Wu, the device of Nakamura/Chen/Chen’565/Kim/Lin/Wu would be able to perform the claimed functions.
Further, Chen recognizes that the composition of the GaN layer underlying the channel layer impacts the absorption and amplifying function of the HEMT-based device. Thus, he composition of the GaN layer underlying the channel layer is a result-effective variable.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to vary, through routine optimization, the composition of the GaN layer underlying the channel layer as Chen has identified the composition of the GaN layer underlying the channel layer as a result-effective variable. Further, a person of ordinary skill in the art would have had a reasonable expectation of success to arrive at a specific composition of the GaN layer underlying the channel layer and appropriately biasing the gate and the drain to have the charge carriers generated by the ionizing radiation passing between the gate and the drain follow a substantially linear path, in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio as taught by Chen (Abstract, pp. 1-4) (MPEP 2144.05).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the HEMT-based device of Nakamura/Chen/Chen’565/Kim/
Lin/Wu by optimizing the GaN buffer layer underlying the channel layer and appropriately biasing the gate and the drain to have the HEMT-based device, wherein, when the device is in operation, the charge carriers generated by the ionizing radiation passing between the gate and the drain follow a substantially linear path, in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio (Chen, Abstract, pp. 1-4).
Regarding claims 15, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura discloses the HEMT-based device, wherein the barrier layer (e.g., 23, InAlGaN) (Nakamura, Fig. 2, ¶0042) is aluminum gallium nitride (AlGaN).
Regarding claims 16, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura discloses the HEMT-based device, wherein the barrier layer (e.g., 23, InAlN) (Nakamura, Fig. 2, ¶0042, ¶0051) is indium aluminum nitride (InAlN).
Regarding claims 17, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura discloses the HEMT-based device, wherein the substrate (10) (Nakamura, Fig. 2, ¶0041) is at least one of silicon carbide (SiC), silicon, sapphire, gallium nitride, and other suitable material.
Claim 5 is rejected under 35 U.S.C. 103 as being unpatentable over US 2018/0047840 to Nakamura in view of Chen (CN 108417662 A), Chen’565 (US 2018/0166565), Kim (US 2004/0046176), Lin (US 2018/0047822), and Wu (US Patent NO. 6,586,781) as applied to claim 1, and further in view of Chen et al. (US 2013/0099243, hereinafter Chen’243).
Regarding claims 5, Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the HEMT-based device of claim 1. Further, Nakamura does not specifically disclose the HEMT-based device, wherein a doping gradient is included in the GaN buffer to enhance sensitivity of the HEMT-based device.
However, Chen teaches forming the GaN buffer layer (103) (Chen, Fig. 1, pp.3-4) underlying the GaN channel layer (104), wherein the GaN buffer layer (103) has a doping concentration of 1015 cm-3 to 1018 cm-3 to absorb radiation (112) to generate electron hole pairs.
Further, Chen’243 teaches forming a HEMT device comprising a buffer layer (Chen’243, Fig. 1, ¶0014-¶0022, ¶0032-¶0033) having varying doping concentration which is graded across the buffer layer to tune the resistivity of the buffer layer, and hence the breakdown voltage of the HEMT device, wherein the doping concentration varies from 1015 cm-3 to 1019 cm-3 (Chen’243, Fig. 1, ¶0018-¶0022).
Thus, Chen’243 recognizes that the doping concentration of the buffer layer impacts the resistivity of the buffer layer and the breakdown voltage of the HEMT device. Thus, the doping concentration in the buffer layer is a result-effective variable.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to vary, through routine optimization, the doping concentration of the buffer layer as Chen’243 has identified the doping concentration as a result-effective variable. Further, a person of ordinary skill in the art would have had a reasonable expectation of success to arrive at a specific doping gradient included in the GaN buffer to enhance sensitivity of the HEMT-based device, in order to tune the resistivity of the buffer layer, and hence the breakdown voltage of the HEMT device as taught by Chen’243 (¶0014, ¶0033) (MPEP 2144.05).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the HEMT-based device of Nakamura/Chen/Chen’565/Kim/
Lin/Wu by optimizing the GaN buffer layer having varying doping concentration as taught by Chen’243 to have the HEMT-based device, wherein a doping gradient is included in the GaN buffer to enhance sensitivity of the HEMT-based device, in order to tune the resistivity of the buffer layer, and hence the breakdown voltage of the HEMT device (Chen’243, ¶0014, ¶0033).
Claims 18-22 are rejected under 35 U.S.C. 103 as being unpatentable CN 108417662 A to Chen in view of Chen’565 (US 2018/0166565) and Kim (US 2004/0046176) (the reference “Review of using gallium nitride for ionizing radiation detection” by Wang et al., (2015) Appl. Phys. Rev. 2, 031102, cited in IDS, hereinafter Wang, is presented as evidence).
With respect to claim 18, Chen discloses an ionizing radiation sensor (e.g., Gallium Nitride-based Radial detector (Chen, Abstract, Fig. 1, pp. 1-4) comprising:
a gallium nitride (GaN) high electron mobility transistor (HEMT) (Chen, Abstract, Fig. 1, pp. 3-4) for receiving high-energy particles (112), the GAN HEMT comprising:
- a source (107), a drain (108) and a gate (109), wherein GaN atoms are ionized, directly or indirectly, to generate charge carriers (e.g., the radiation 112 is absorbed in the GaN buffer layer 103 underlying the GaN channel layer 104 and is converted into electric signal that is amplified by self-signal amplifying function of GaN detector, and transmitted to high electron transport efficiency transistor output) as radiation travels through the GaN HEMT; and
a backside terminal (101) to which a bias can be applied to enhance collection of the charge carriers.
Further, Chen does not specifically disclose a multiplication region at the gate, wherein the charge carriers are collected to generate a signal through application of lateral electric fields thereby collecting, and when suitably biased, amplifying the signal via impact ionization near a gate edge.
Further, the recitations of claim 18 "a bias can be applied to enhance collection of charge carriers" are intended-use recitations. Note that a recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim. See, e.g., In re Pearson, 181 USPQ 641 (CCPA); In re Minks, 169 USPQ 120 (Bd Appeals); In re Casey, 152 USPQ 235 (CCPA 1967); In re Otto, 136 USPQ 458, 459 (CCPA 1963). See MPEP §2114.
However, Chen’565 teaches that when the HEMT transistor structure (Chen’565, Fig. 1L, ¶0003, ¶0015-¶0039) is operated in high power devices, a high electric field occurs at the gate-to-drain region (Chen’565, Fig. 1L, ¶0039), and the gate operation voltage of the HEMT device is controlled to provide desired performance of the HEMT transistor.
Further, Kim teaches forming avalanche phototransistor (Kim, Fig. 1, ¶0003, ¶0025-¶0032, ¶0059), wherein the electrons created in the photo-absorption layer are multiplicated by impact ionization occurred in the multiplication layer due to a very high electric field effect, and the avalanche gain by the impact ionization effect is obtained (Kim, Fig. 1, ¶0059).
Thus, a person of ordinary skill in the art would recognize that a high electric field occurred at the gate-to-drain region of the HEMT transistor as taught by Chen’565, wherein the HEMT transistor is configured for radiation detection as taught by Chen, would result in multiplication of electrons by impact ionization due to a very high electric field effect as taught by Kim, to provide high performance photo-transistor.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the radiation sensor of Chen by controlling the gate operation voltage of the HEMT device to control a high electric field occurred at the gate-to-drain region as taught by Chen’565, wherein the electrons created in the photo-absorption layer of Chen/Chen’565 are multiplied by impact ionization due to a very high electric field effect as taught by Kim to have the ionizing radiation sensor comprising: a multiplication region at the gate, wherein the charge carriers are collected to generate a signal through application of lateral electric fields thereby collecting, and when suitably biased, amplifying the signal via impact ionization near a gate edge, in order to control operation of the HEMT-based device having high mobility; to provide high performance photo-transistor; and to obtain improved radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio (Chen’565, ¶0003, ¶0015, ¶0039; Kim, ¶0008-¶0009, ¶0059; Chen, Abstract, pp. 1-3).
Regarding claims 19 and 20, Chen in view of Chen’565 and Kim discloses the sensor of claim 18. Further, Chen does not specifically disclose that the high-energy particles are beta- particles (as claimed in claim 19); wherein the high-energy particles are alpha- particles (as claimed in claim 20).
However, Chen discloses that the Gallium Nitride-based Radial detector (Chen, Abstract, Fig. 1, pp. 1-4) comprising high electron mobility transistor (HEMT) is used for radiation detection, cosmic ray detection, high energy accelerated particle collision product detection, nuclear fission/fusion to radiation detection.
Further, it is known in the art (e.g., as evidenced by Wang, Abstract, pp. 031102-1 to 1031102-6) that GaN as a wide band-gap semiconductor material having properties such as large displacement energy and high thermal stability is used to detect alpha particles, X-rays, and for beta particles response.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the sensor of Chen/Chen’565/Kim by absorbing the radiation including high energy accelerated particles as taught by Chen to have the sensor, wherein the high-energy particles are beta- particles (as claimed in claim 19); wherein the high-energy particles are alpha- particles (as claimed in claim 20), in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio (Chen, Abstract, pp. 1-3).
Regarding claim 21, Chen in view of Chen’565 and Kim discloses the sensor of claim 18. Further, Chen does not specifically disclose that the lateral electric fields amplify the signal without the GaN HEMT undergoing breakdown.
However, Chen’565 teaches that a high electric field occurs at the gate-to-drain region (Chen’565, Fig. 1L, ¶0039) of the HEMT transistor.
Further, Kim teaches forming avalanche phototransistor (Kim, Fig. 1, ¶0003, ¶0025-¶0032, ¶0059), wherein the electrons created in the photo-absorption layer are multiplicated by impact ionization occurred in the multiplication layer due to a very high electric field effect, and the avalanche gain by the impact ionization effect is obtained (Kim, Fig. 1, ¶0059).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the invention to modify the radiation sensor of Chen/Chen’565/Kim by controlling the gate operation voltage of the HEMT device to control a high electric field occurred at the gate-to-drain region as taught by Chen’565, wherein the electrons created in the photo-absorption layer of Chen/Chen’565/Kim are multiplied by impact ionization due to a very high electric field effect as taught by Kim to have the sensor, wherein the lateral electric fields amplify the signal without the GaN HEMT undergoing breakdown, in order to control operation of the HEMT-based device having high mobility; to provide high performance photo-transistor; and thus to obtain improved radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio (Chen’565, ¶0039; Kim, ¶0008, ¶0009, ¶0059; Chen, Abstract, pp. 1-3).
Regarding claim 22, Chen in view of Chen’565 and Kim discloses the sensor of claim 18. Further, Chen discloses the sensor, comprising a multiplication region (e.g., the radiation 112 is absorbed in the GaN buffer layer 103 underlying the GaN channel layer 104 and is converted into electric signal that is amplified by self-signal amplifying function of GaN detector) adapted to achieve an acceptable signal to noise ratio (SNR) (Chen, Abstract, pp. 1-4).
Response to Arguments
Applicant's arguments filed 04/10/2026 have been fully considered but they are not persuasive.
In response to Applicant's arguments against the references individually (“There is no description in Nakamura of a HEMT comprising a backside terminal”, “There is no multiplication at the gate edge due to the high electric field”, “Chen'565 neither describes nor suggests the presence of a backside terminal, as specified by claim 1”, “[n]o motivation for a person of skill in the art to combine Kim with Chen and Chen'565 when considering how to produce a HEMT-based device for detecting ionizing radiation”, and “Neither Lin nor Wu describes a HEMT configured to detect ionizing ration wherein the device comprises a backside terminal”), the examiner submits that one cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986).
In the instant case, Chen discloses forming a backside terminal (101) to facilitate absorbing the radiation (112) in the GaN buffer layer 103 underlying the GaN channel layer 104.
The combination Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu discloses the structure as claimed in claim 1. Thus, the structure of Nakamura/Chen/Chen’565/Kim/Lin/Wu would be capable of detecting ionizing radiation as claimed in claim 1.
In response to applicant’s argument that there is no teaching, suggestion, or motivation to combine the references (“[n]o motivation for a person of skill in the art to combine Kim with Chen and Chen'565 when considering how to produce a HEMT-based device for detecting ionizing radiation”), the examiner recognizes that obviousness may be established by combining or modifying the teachings of the prior art to produce the claimed invention where there is some teaching, suggestion, or motivation to do so found either in the references themselves or in the knowledge generally available to one of ordinary skill in the art. See In re Fine, 837 F.2d 1071, 5 USPQ2d 1596 (Fed. Cir. 1988), In re Jones, 958 F.2d 347, 21 USPQ2d 1941 (Fed. Cir. 1992), and KSR International Co. v. Teleflex, Inc., 550 U.S. 398, 82 USPQ2d 1385 (2007).
In this case, a person of ordinary skill in the art would recognize configuring the HEMT transistor of Nakamura to detect radiation by forming a GaN buffer under GaN channel and a back electrode as taught by Chen, and controlling the gate operation voltage of the HEMT device to control a high electric field occurred at the gate-to-drain region as taught by Chen’565, wherein the electrons created in the photo-absorption layer of Nakamura/Chen/ Chen’565 are multiplied by impact ionization due to a very high electric field effect as taught by Kim to have a semiconductor HEMT-based device as claimed in claim 1, in order to provide GaN-based HEMT radial detector having signal amplifying function and advantages of high sensitivity, fast response speed, and high signal-to-noise ratio; to control operation of the HEMT-based device having high mobility; and to provide high performance photo-transistor (Chen, Abstract, pp. 1-3; Chen’565, ¶0003, ¶0015, ¶0039; Kim, ¶0008-¶0009, ¶0059).
In response to applicant’s argument that “[c]laim 1 is directed to a HEMT device with a basic structure that does not require any p-n junctions to aid in carrier collection”, the examiner submits that claim language does not exclude GaN HEMT device comprising GaN buffer layer including a p-n junction.
In response to applicant's argument that “[n]one of Chen, Chen'565, and Kim, either individually or in combination, describes or suggests an ionizing radiation sensor comprising a GaN HEMT comprising a backside terminal to which a bias can be applied to enhance collection of charge carriers”, the examiner submits that the recitations of claim 1 "a bias can be applied to enhance collection of charges generated in the bulk of the device by directing them vertically towards the GaN channel layer" are intended-use recitations, and a recitation of the intended use of the claimed invention must result in a structural difference between the claimed invention and the prior art in order to patentably distinguish the claimed invention from the prior art. If the prior art structure is capable of performing the intended use, then it meets the claim. In the instant case, the structure of Nakamura/Chen/Chen’565/Kim/Lin/Wu would be capable of detecting ionizing radiation as claimed in claim 1.
Therefore, the above Applicant's arguments are not persuasive, and the rejection of claim 1 under 35 USC 103 over Nakamura in view of Chen, Chen’565, Kim, Lin, and Wu, and the rejection of claim 18 under 35 USC 103 over Chen in view of Chen’565 and Kim are maintained.
Regarding dependent claims 2-17 and 19-22 which depend on the independent claims 1 and 18, the examiner respectfully submits that the applicant’s arguments with respect to dependent claims are not persuasive for the above reasons, thus, the rejections of the dependent claims are sustained.
Conclusion
THIS ACTION IS MADE FINAL. Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to NATALIA GONDARENKO whose telephone number is (571)272-2284. The examiner can normally be reached 9:30 AM-7:30 PM.
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/NATALIA A GONDARENKO/Primary Examiner, Art Unit 2891
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