The high-temperature performance of 4H-SiC ultraviolet avalanche photodiodes(APDs)in both linear and Geiger modes is extensively investigated.During the temperature-dependent measurements,a fixed bias voltage is adopt...The high-temperature performance of 4H-SiC ultraviolet avalanche photodiodes(APDs)in both linear and Geiger modes is extensively investigated.During the temperature-dependent measurements,a fixed bias voltage is adopted for the device samples,which is much more practical and important for high-temperature applications.The results show that the fabricated 4H-SiC APDs are very stable and reliable at high temperatures.As the temperature increases from room temperature to 425 K,the dark current at 95%of the breakdown voltage increases slightly and remains lower than40 pA.In Geiger mode,our 4H-SiC APDs can be self-quenched in a passive-quenching circuit,which is expected for highspeed detection systems.Moreover,an interesting phenomenon is observed for the first time:the single-photon detection efficiency shows a non-monotonic variation as a function of temperature.The physical mechanism of the variation in hightemperature performance is further analyzed.The results in this work can provide a fundamental reference for researchers in the field of 4H-SiC APD ultraviolet detectors.展开更多
In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor （LBJT） with a base tield plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the ...In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor （LBJT） with a base tield plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the base region is restricted by the base field plate. Thin base as well as low base doping of the LBJT therefore can be achieved under the condition of avalanche breakdown. Simulation results show that thin base of 0.32 μm and base doping of 3 × 1017 cm 3 are obtained, and corresponding current gain is as high as 247 with avalanche breakdown voltage of 3309 V when the drift region length is 30 μm. Besides, an investigation of a 4H-SiC vertical BJT （VBJT） with comparable breakdown voltage （3357 V） shows that the minimum base width of 0.25 ~tm and base doping as high as 8 × 10^17 cm^-3 contribute to a maximum current gain of only 128.展开更多
This paper presents the development of lateral depletion-mode n-channel 4 H-SiC junction field-effect transistors(LJFETs)using double-mesa process toward high-temperature integrated circuit(IC)applications.At room tem...This paper presents the development of lateral depletion-mode n-channel 4 H-SiC junction field-effect transistors(LJFETs)using double-mesa process toward high-temperature integrated circuit(IC)applications.At room temperature,the fabricated LJFETs show a drain-to-source saturation current of 23.03μA/μm,which corresponds to a current density of 7678 A/cm^(2).The gate-to-source parasitic resistance of 17.56 kΩ·μm is reduced to contribute only 13.49%of the on-resistance of 130.15 kΩ·μm,which helps to improve the transconductance up to 8.61μS/μm.High temperature characteristics of LJFETs were performed from room temperature to 400℃.At temperatures up to 400℃in air,it is observed that the fabricated LJFETs still show normally-on operating characteristics.The drain-to-source saturation current,transconductance and intrinsic gain at 400℃are 7.47μA/μm,2.35μS/μm and 41.35,respectively.These results show significant improvement over state-of-the-art and make them attractive for high-temperature IC applications.展开更多
We study a series of（HfO2）x（Al2O3）1-x /4H-SiC MOS capacitors. It is shown that the conduction band offset of HfO2 is 0.5 e V and the conduction band offset of Hf AlO is 1.11–1.72 e V. The conduction band offsets...We study a series of（HfO2）x（Al2O3）1-x /4H-SiC MOS capacitors. It is shown that the conduction band offset of HfO2 is 0.5 e V and the conduction band offset of Hf AlO is 1.11–1.72 e V. The conduction band offsets of（Hf O2）x（Al2O3）1-x are increased with the increase of the Al composition, and the（HfO2）x（Al2O3）1-x offer acceptable barrier heights（〉 1 e V）for both electrons and holes. With a higher conduction band offset,（Hf O2）x（Al2O3）1-x/4H-SiC MOS capacitors result in a ～ 3 orders of magnitude lower gate leakage current at an effective electric field of 15 MV/cm and roughly the same effective breakdown field of ～ 25 MV/cm compared to HfO2. Considering the tradeoff among the band gap, the band offset, and the dielectric constant, we conclude that the optimum Al2O3 concentration is about 30% for an alternative gate dielectric in 4H-Si C power MOS-based transistors.展开更多
Owing to the conductivity modulation of silicon carbide（Si C） bipolar devices, n-channel insulated gate bipolar transistors（n-IGBTs） have a significant advantage over metal oxide semiconductor field effect transis...Owing to the conductivity modulation of silicon carbide（Si C） bipolar devices, n-channel insulated gate bipolar transistors（n-IGBTs） have a significant advantage over metal oxide semiconductor field effect transistors（MOSFETs） in ultra high voltage（UHV） applications. In this paper, backside grinding and laser annealing process were carried out to fabricate 4 H-Si C n-IGBTs. The thickness of a drift layer was 120 μm, which was designed for a blocking voltage of 13 k V. The n-IGBTs carried a collector current density of 24 A/cm^2 at a power dissipation of300 W/cm^2 when the gate voltage was 20 V, with a differential specific on-resistance of 140 mΩ·cm^2.展开更多
An improved dual-channel 4H-SiC MESFET with high doped n-type surface layer and step-gate structure is proposed, and the static and dynamic electrical performances are analyzed.A high doped n-type surface layer is app...An improved dual-channel 4H-SiC MESFET with high doped n-type surface layer and step-gate structure is proposed, and the static and dynamic electrical performances are analyzed.A high doped n-type surface layer is applied to obtain a low source parasitic series resistance, while the step-gate structure is utilized to reduce the gate capacitance by the elimination of the depletion layer extension near the gate edge, thereby improving the RF characteristics and still maintaining a high breakdown voltage and a large drain current in comparison with the published SiC MESFETs with a dual-channel layer.Detailed numerical simulations demonstrate that the gate-to-drain capacitance, the gate-to-source capacitance, and the source parasitic series resistance of the proposed structure are about 4%, 7%, and 18% smaller than those of the dual-channel structure, which is responsible for 1.4 and 6 GHz improvements in the cut-off frequency and the maximum oscillation frequency.展开更多
Based on the material characteristics and the operational principle of the double base epilayer BJTs,and according to the drift-diffusion and the carrier recombination theory,the common emitter current gain is calcula...Based on the material characteristics and the operational principle of the double base epilayer BJTs,and according to the drift-diffusion and the carrier recombination theory,the common emitter current gain is calculated considering four recombination processes.Then its performance is analyzed under high temperature conditions.The results show that the emitter injection efficiency decreases due to an increase in the base ionization rate with increasing temperature.Meanwhile,the SiC/SiO2 interface states and the quality of the passivation layer will affect the surface recombination velocity,and make an obvious current gain fall-off at a high collector current.展开更多
SILICON carbide, a semiconductor with chemistry inertia, is well suited to fabricate optoelectronic device working at high temperature, high power, high frequency, and in high radiation environments. Among the hundred...SILICON carbide, a semiconductor with chemistry inertia, is well suited to fabricate optoelectronic device working at high temperature, high power, high frequency, and in high radiation environments. Among the hundreds of SiC polytypes, 4H-SiC, with a wider bandgap, a higher and much less anisotropic electron mobility than 6H-SiC, has aroused much attention .展开更多
Most of the natural occurring radionuclides in both noodles and bread are found to have specific activities below the detectable limit of the high purity germanium (n-type) spectrometer system of the EG&G Ortec C...Most of the natural occurring radionuclides in both noodles and bread are found to have specific activities below the detectable limit of the high purity germanium (n-type) spectrometer system of the EG&G Ortec Company. For dried bread, 40K,137Cs and 60Co are found to be 44.45￣84.52, < 0.012 ￣0.052, < 0.018 ￣0.054 Bq/kg;for noodles, to be 29.55￣64.54, < 0.01 ￣0.069 and < 9.8× 10-3 ￣ 0.074 Bq/kg,respectively. The weighted committed dose equivalents due to the ingestion of 137Csfrom noodles and bread for a male and female adults have been estimated to be 0.5and 0.6μSv, respectively, being less than the values recommended by ICRP.展开更多
基金the National Natural Science Foundation of China(Grant No.61974134)Hebei Province Outstanding Youth Fund(Grant No.F2021516001).
文摘The high-temperature performance of 4H-SiC ultraviolet avalanche photodiodes(APDs)in both linear and Geiger modes is extensively investigated.During the temperature-dependent measurements,a fixed bias voltage is adopted for the device samples,which is much more practical and important for high-temperature applications.The results show that the fabricated 4H-SiC APDs are very stable and reliable at high temperatures.As the temperature increases from room temperature to 425 K,the dark current at 95%of the breakdown voltage increases slightly and remains lower than40 pA.In Geiger mode,our 4H-SiC APDs can be self-quenched in a passive-quenching circuit,which is expected for highspeed detection systems.Moreover,an interesting phenomenon is observed for the first time:the single-photon detection efficiency shows a non-monotonic variation as a function of temperature.The physical mechanism of the variation in hightemperature performance is further analyzed.The results in this work can provide a fundamental reference for researchers in the field of 4H-SiC APD ultraviolet detectors.
基金supported by the Ministry of Education of China (Grant No. 20100101110056)the Natural Science Foundation for Distinguished Young Scholars of Zhejiang Province of China (Grant No. R1100468)
文摘In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor （LBJT） with a base tield plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the base region is restricted by the base field plate. Thin base as well as low base doping of the LBJT therefore can be achieved under the condition of avalanche breakdown. Simulation results show that thin base of 0.32 μm and base doping of 3 × 1017 cm 3 are obtained, and corresponding current gain is as high as 247 with avalanche breakdown voltage of 3309 V when the drift region length is 30 μm. Besides, an investigation of a 4H-SiC vertical BJT （VBJT） with comparable breakdown voltage （3357 V） shows that the minimum base width of 0.25 ~tm and base doping as high as 8 × 10^17 cm^-3 contribute to a maximum current gain of only 128.
基金Project supported by the Key Research and Development Program of Shaanxi Province,China(Grant No.2020ZDLGY03-07)the National Science Foundation of China(Grant Nos.61774117 and 61774119)+4 种基金the Science Challenge Project(Grant No.TZ2018003)the National Key R&D Program of China(Grant No.2017YFB0102302)the Shaanxi Science&Technology Nova Program,China(Grant No.2019KJXX-029)the Key-Area Research and Development Program of Guang Dong Province,China(Grant No.2020B010170001)the Fundamental Research Funds for the Central Universities,China(Grant No.5012-20106205935)。
文摘This paper presents the development of lateral depletion-mode n-channel 4 H-SiC junction field-effect transistors(LJFETs)using double-mesa process toward high-temperature integrated circuit(IC)applications.At room temperature,the fabricated LJFETs show a drain-to-source saturation current of 23.03μA/μm,which corresponds to a current density of 7678 A/cm^(2).The gate-to-source parasitic resistance of 17.56 kΩ·μm is reduced to contribute only 13.49%of the on-resistance of 130.15 kΩ·μm,which helps to improve the transconductance up to 8.61μS/μm.High temperature characteristics of LJFETs were performed from room temperature to 400℃.At temperatures up to 400℃in air,it is observed that the fabricated LJFETs still show normally-on operating characteristics.The drain-to-source saturation current,transconductance and intrinsic gain at 400℃are 7.47μA/μm,2.35μS/μm and 41.35,respectively.These results show significant improvement over state-of-the-art and make them attractive for high-temperature IC applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.51272202 and 61234006)the Science Project of State Grid,China(Grant No.SGRI-WD-71-14-004)
文摘We study a series of（HfO2）x（Al2O3）1-x /4H-SiC MOS capacitors. It is shown that the conduction band offset of HfO2 is 0.5 e V and the conduction band offset of Hf AlO is 1.11–1.72 e V. The conduction band offsets of（Hf O2）x（Al2O3）1-x are increased with the increase of the Al composition, and the（HfO2）x（Al2O3）1-x offer acceptable barrier heights（〉 1 e V）for both electrons and holes. With a higher conduction band offset,（Hf O2）x（Al2O3）1-x/4H-SiC MOS capacitors result in a ～ 3 orders of magnitude lower gate leakage current at an effective electric field of 15 MV/cm and roughly the same effective breakdown field of ～ 25 MV/cm compared to HfO2. Considering the tradeoff among the band gap, the band offset, and the dielectric constant, we conclude that the optimum Al2O3 concentration is about 30% for an alternative gate dielectric in 4H-Si C power MOS-based transistors.
文摘Owing to the conductivity modulation of silicon carbide（Si C） bipolar devices, n-channel insulated gate bipolar transistors（n-IGBTs） have a significant advantage over metal oxide semiconductor field effect transistors（MOSFETs） in ultra high voltage（UHV） applications. In this paper, backside grinding and laser annealing process were carried out to fabricate 4 H-Si C n-IGBTs. The thickness of a drift layer was 120 μm, which was designed for a blocking voltage of 13 k V. The n-IGBTs carried a collector current density of 24 A/cm^2 at a power dissipation of300 W/cm^2 when the gate voltage was 20 V, with a differential specific on-resistance of 140 mΩ·cm^2.
基金supported by the State Key Development Program for Basic Research of China(No.51327010101)
文摘An improved dual-channel 4H-SiC MESFET with high doped n-type surface layer and step-gate structure is proposed, and the static and dynamic electrical performances are analyzed.A high doped n-type surface layer is applied to obtain a low source parasitic series resistance, while the step-gate structure is utilized to reduce the gate capacitance by the elimination of the depletion layer extension near the gate edge, thereby improving the RF characteristics and still maintaining a high breakdown voltage and a large drain current in comparison with the published SiC MESFETs with a dual-channel layer.Detailed numerical simulations demonstrate that the gate-to-drain capacitance, the gate-to-source capacitance, and the source parasitic series resistance of the proposed structure are about 4%, 7%, and 18% smaller than those of the dual-channel structure, which is responsible for 1.4 and 6 GHz improvements in the cut-off frequency and the maximum oscillation frequency.
基金Project supported by the National Natural Science Foundation of China(No.60876061)the Key Laboratory Foundation of China (No.20090C1403)
文摘Based on the material characteristics and the operational principle of the double base epilayer BJTs,and according to the drift-diffusion and the carrier recombination theory,the common emitter current gain is calculated considering four recombination processes.Then its performance is analyzed under high temperature conditions.The results show that the emitter injection efficiency decreases due to an increase in the base ionization rate with increasing temperature.Meanwhile,the SiC/SiO2 interface states and the quality of the passivation layer will affect the surface recombination velocity,and make an obvious current gain fall-off at a high collector current.
文摘SILICON carbide, a semiconductor with chemistry inertia, is well suited to fabricate optoelectronic device working at high temperature, high power, high frequency, and in high radiation environments. Among the hundreds of SiC polytypes, 4H-SiC, with a wider bandgap, a higher and much less anisotropic electron mobility than 6H-SiC, has aroused much attention .
文摘Most of the natural occurring radionuclides in both noodles and bread are found to have specific activities below the detectable limit of the high purity germanium (n-type) spectrometer system of the EG&G Ortec Company. For dried bread, 40K,137Cs and 60Co are found to be 44.45￣84.52, < 0.012 ￣0.052, < 0.018 ￣0.054 Bq/kg;for noodles, to be 29.55￣64.54, < 0.01 ￣0.069 and < 9.8× 10-3 ￣ 0.074 Bq/kg,respectively. The weighted committed dose equivalents due to the ingestion of 137Csfrom noodles and bread for a male and female adults have been estimated to be 0.5and 0.6μSv, respectively, being less than the values recommended by ICRP.
