A1GaN/GaN depletion-mode high-electron-mobility transistor （D-HEMT） and fluorine （F） plasma treated enhancement-mode high-electron-mobility transistor （E-HEMT） are exposed to 60Co gamma radiation with a dose of ...A1GaN/GaN depletion-mode high-electron-mobility transistor （D-HEMT） and fluorine （F） plasma treated enhancement-mode high-electron-mobility transistor （E-HEMT） are exposed to 60Co gamma radiation with a dose of 1.6 Mrad （Si）. No degradation is observed in the performance of D-HEMT. However, the maximum transeonductance of E-HEMT is increased after radiation. The 2DEG density and the mobility are calculated from the results of capacitance-voltage measurement. The electron mobility decreases after fluorine plasma treatment and recovers after radiation. Conductance measurements in a frequency range from 10 kHz to 1 MHz are used to characterize the trapping effects in the devices. A new type of trap is observed in the F plasma treated E-HEMT compared with the D-HEMT, but the density of the trap decreases by radiation. Fitting of Gp/w data yields the trap densities DT = （1-3）Х1012 cm^-2.eV^-1 and DT = （0,2-0.8）Х10^12 cm^2-eV^-1 before and after radiation, respectively. The time constant is 0.5 ms-6 ms. With F plasma treatment, the trap is introduced by etch damage and degrades the electronic mobility. After 60Co gamma radiation, the etch damage decreases and the electron mobility is improved. The gamma radiation can recover the etch damage caused by F plasma treatment.展开更多
This paper reports fluorine plasma treatment enhancement-mode HEMTs （high electronic mobility transistors） EHEMTs and conventional depletion-mode HEMTs DHEMTs fabricated on one wafer using separate litho-photography...This paper reports fluorine plasma treatment enhancement-mode HEMTs （high electronic mobility transistors） EHEMTs and conventional depletion-mode HEMTs DHEMTs fabricated on one wafer using separate litho-photography technology. It finds that fluorine plasma etches the AlGaN at a slow rate by capacitance-voltage measurement. Using capacitance-frequency measurement, it finds one type of trap in conventional DHEMTs with TT = （0.5 - 6） ms and DT ： （1 - 5）×10^13 cm^-2. eV^-1. Two types of trap are found in fluorine plasma treatment EHEMTs, fast with TW（f）= （0.2 - 2） μs and slow with TT（s） = （0.5 - 6） ms. The density of trap states evaluated on the EHEMTs is Dw（f） ： （1 - 3） × 10^12 cm^-2. eV^-1 and DT（s） =（2 - 6） × 10^12 cm-2. eV-1 for the fast and slow traps, respectively. The result shows that the fluorine plasma treatment reduces the slow trap density by about one order, but introduces a new type of fast trap. The slow trap is suggested to be a surface trap, related to the gate leakage current.展开更多
The effects of ^60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electron- mobility transistors （E-mode HEMTs） are investigated. The results show that having been irradiated by^60...The effects of ^60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electron- mobility transistors （E-mode HEMTs） are investigated. The results show that having been irradiated by^60Co γ-rays at a dose of 3 Mrad （Si）, the E-mode HEMT reduces its saturation drain current and maximal transconductance by 6% and 5%, respectively, and significantly increases both forward and reverse gate currents, while its threshold voltage is affected only slightly. The obvious performance degradation of E-mode A1GaN/GaN HEMTs is consistent with the creation of electronegative surface state charges in the source-gate spacer and gate-drain spacer after being irradiated.展开更多
Pulsed metal organic chemical vapor deposition was employed to grow nearly polarization matched InAlGaN/GaN heterostructures. A relatively low sheet carrier density of 1.8×10^(12)cm^(-2), together with a high ele...Pulsed metal organic chemical vapor deposition was employed to grow nearly polarization matched InAlGaN/GaN heterostructures. A relatively low sheet carrier density of 1.8×10^(12)cm^(-2), together with a high electron mobility of1229.5 cm^2/V·s, was obtained for the prepared heterostructures. The surface morphology of the heterostructures was also significantly improved, i.e., with a root mean square roughness of 0.29 nm in a 2 μm×2 μm scan area. In addition to the improved properties, the enhancement-mode metal–oxide–semiconductor high electron mobility transistors(MOSHEMTs) processed on the heterostructures not only exhibited a high threshold voltage(VTH) of 3.1 V, but also demonstrated a significantly enhanced drain output current density of 669 m A/mm. These values probably represent the largest values obtained from the InAlGaN based enhancement-mode devices to the best of our knowledge. This study strongly indicates that the InAlGaN/GaN heterostructures grown by pulsed metal organic chemical vapor deposition could be promising for the applications of novel nitride-based electronic devices.展开更多
Ultra-thin barrier(UTB) 4-nm-Al Ga N/Ga N normally-off high electron mobility transistors(HEMTs) having a high current gain cut-off frequency( fT) are demonstrated by the stress-engineered compressive Si N trench tech...Ultra-thin barrier(UTB) 4-nm-Al Ga N/Ga N normally-off high electron mobility transistors(HEMTs) having a high current gain cut-off frequency( fT) are demonstrated by the stress-engineered compressive Si N trench technology.The compressive in-situ Si N guarantees the UTB-Al Ga N/Ga N heterostructure can operate a high electron density of1.27×1013 cm-2, a high uniform sheet resistance of 312.8 Ω/, but a negative threshold for the short-gate devices fabricated on it. With the lateral stress-engineering by full removing in-situ Si N in the 600-nm Si N trench, the short-gated(70 nm) devices obtain a threshold of 0.2 V, achieving the devices operating at enhancement-mode(E-mode). Meanwhile,the novel device also can operate a large current of 610 m A/mm and a high transconductance of 394 m S/mm for the Emode devices. Most of all, a high fT/fmax of 128 GHz/255 GHz is obtained, which is the highest value among the reported E-mode Al Ga N/Ga N HEMTs. Besides, being together with the 211 GHz/346 GHz of fT/fmax for the D-mode HEMTs fabricated on the same materials, this design of E/D-mode with the realization of fmax over 200 GHz in this work is the first one that can be used in Q-band mixed-signal application with further optimization. And the minimized processing difference between the E-and D-mode designs the addition of the Si N trench, will promise an enormous competitive advantage in the fabricating costs.展开更多
A novel groove-type channel enhancement-mode AlGaN/GaN MIS high electron mobility transistor（GTCE-HEMT）with a combined polar and nonpolar AlGaN/GaN heterostucture is presented. The device simulation shows a threshol...A novel groove-type channel enhancement-mode AlGaN/GaN MIS high electron mobility transistor（GTCE-HEMT）with a combined polar and nonpolar AlGaN/GaN heterostucture is presented. The device simulation shows a threshold voltage of 1.24 V, peak transconductance of 182 m S/mm, and subthreshold slope of 85 m V/dec, which are obtained by adjusting the device parameters. Interestingly, it is possible to control the threshold voltage accurately without precisely controlling the etching depth in fabrication by adopting this structure. Besides, the breakdown voltage（VB） is significantly increased by 78% in comparison with the value of the conventional MIS-HEMT. Moreover, the fabrication process of the novel device is entirely compatible with that of the conventional depletion-mode（D-mode） polar AlGaN/GaN HEMT. It presents a promising way to realize the switch application and the E/D-mode logic circuits.展开更多
When using traditional drive circuits,the enhancement-mode GaN(eGaN)HEMT will be affected by high switching speed characteristics and parasitic parameters leading to worse crosstalk problems.Currently,the existing cro...When using traditional drive circuits,the enhancement-mode GaN(eGaN)HEMT will be affected by high switching speed characteristics and parasitic parameters leading to worse crosstalk problems.Currently,the existing crosstalk suppression drive circuits often have the disadvantages of increased switching loss,control complexity,and overall electromagnetic interference(EMI).Therefore,this paper combines the driving loop impedance control and the active Miller clamp method to propose an improved active Miller clamp drive circuit.First,the crosstalk mechanism is analyzed,and the crosstalk voltage model is established.Through the crosstalk voltage evaluation platform,the influencing factors are evaluated experimentally.Then,the operating principle of the improved active Miller clamp drive circuit is discussed,and the optimized parameter design method is given.Finally,the effect of the improved active Miller clamp method for suppressing crosstalk is experimentally verified.The crosstalk voltage was suppressed from 3.5 V and-3.5 V to 1 V and-1.3 V,respectively,by the improved circuit.展开更多
Two types of enhancement-mode(E-mode)AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors(MIS-HEMTs)with different gate insulators are fabricated on Si substrates.The HfO2 gate insulator and the ...Two types of enhancement-mode(E-mode)AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors(MIS-HEMTs)with different gate insulators are fabricated on Si substrates.The HfO2 gate insulator and the Al2O3 gate insulator each with a thickness of 30 nm are grown by the plasma-enhanced atomic layer deposition(PEALD).The energy band diagrams of two types of dielectric MIS-HEMTs are compared.The breakdown voltage(VBR)of HfO2 dielectric layer and Al2O3 dielectric layer are 9.4 V and 15.9 V,respectively.With the same barrier thickness,the transconductance of MIS-HEMT with HfO2 is larger.The threshold voltage(Vth)of the HfO2 and Al2O3 MIS-HEMT are 2.0 V and 2.4 V,respectively,when the barrier layer thickness is 0 nm.The C-V characteristics are in good agreement with the Vth's transfer characteristics.As the barrier layer becomes thinner,the drain current density decreases sharply.Due to the dielectric/AlGaN interface is very close to the channel,the scattering of interface states will lead the electron mobility to decrease.The current collapse and the Ron of Al2O3 MIS-HEMT are smaller at the maximum gate voltage.As Al2O3 has excellent thermal stability and chemical stability,the interface state density of Al2O3/AlGaN is less than that of HfO2/AlGaN.展开更多
A non-recessed-gate quasi-E-mode double heterojunction A1GaN/GaN high electron mobility transistor （quasi-E- DHEMT） with a thin barrier, high breakdown voltage and good performance of drain induced barrier lowering ...A non-recessed-gate quasi-E-mode double heterojunction A1GaN/GaN high electron mobility transistor （quasi-E- DHEMT） with a thin barrier, high breakdown voltage and good performance of drain induced barrier lowering （DIBL） was presented. Due to the metal organic chemical vapor deposition （MOCVD） grown 9-nm undoped A1GaN barrier, the effect that the gate metal depleted the two-dimensiomal electron gas （2DEG） was greatly impressed. Therefore, the density of carriers in the channel was nearly zero. Hence, the threshold voltage was above 0 V. Quasi-E-DHEMT with 4.1%tm source-to-drain distance, 2.6-μm gate-to-drain distance, and 0.5-μm gate length showed a drain current of 260 mA/mm. The threshold voltage of this device was 0.165 V when the drain voltage was 10 V and the DIBL was 5.26 mV/V. The quasi-E-DHEMT drain leakage current at a drain voltage of 146 V and a gate voltage of -6 V was below 1 mA/mm. This indicated that the hard breakdown voltage was more than 146 V.展开更多
In this paper,an interleaved LCLC converter with enhancement-mode(E-mode)GaN devices is introduced to achieve the accurate current sharing performance for data center applications. Any tolerance in the resonant tank e...In this paper,an interleaved LCLC converter with enhancement-mode(E-mode)GaN devices is introduced to achieve the accurate current sharing performance for data center applications. Any tolerance in the resonant tank elements can lead to large load imbalance between any two different phases. Due to the steep gain curves of LCLC converters,conventional current sharing methods are not effective. In the proposed converter,the impedances of the resonant networks are matched by switching a capacitor,i.e.,switch controlled capacitor(SCC),in series with the resonant capacitor in one or some of the phases,which results in accurate load current sharing among the phases with an accuracy around 0.025%. The load share of a phase is sensed through the resonant current on it,and the control logic applied to such current sharing can be achieved. By this method,accurate current sharing is achieved for a wide input voltage range required for the hold-up time in data center applications. Interleaving is applied in the proposed multiphase LCLC converter,resulting in low current stress on the output capacitor and allowing ceramic capacitor implementation. Moreover,phase shedding accomplishes high light load efficiency. The performance of the proposed interleaved LCLC converter is verified by a two-phase 1 k W prototype with an input voltage ranging from 250 V to 400 V and a fixed 12 V output voltage.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 60736033)the Fundamental Research Funds for the Central Universities,China (Grant No. JY10000904009)
文摘A1GaN/GaN depletion-mode high-electron-mobility transistor （D-HEMT） and fluorine （F） plasma treated enhancement-mode high-electron-mobility transistor （E-HEMT） are exposed to 60Co gamma radiation with a dose of 1.6 Mrad （Si）. No degradation is observed in the performance of D-HEMT. However, the maximum transeonductance of E-HEMT is increased after radiation. The 2DEG density and the mobility are calculated from the results of capacitance-voltage measurement. The electron mobility decreases after fluorine plasma treatment and recovers after radiation. Conductance measurements in a frequency range from 10 kHz to 1 MHz are used to characterize the trapping effects in the devices. A new type of trap is observed in the F plasma treated E-HEMT compared with the D-HEMT, but the density of the trap decreases by radiation. Fitting of Gp/w data yields the trap densities DT = （1-3）Х1012 cm^-2.eV^-1 and DT = （0,2-0.8）Х10^12 cm^2-eV^-1 before and after radiation, respectively. The time constant is 0.5 ms-6 ms. With F plasma treatment, the trap is introduced by etch damage and degrades the electronic mobility. After 60Co gamma radiation, the etch damage decreases and the electron mobility is improved. The gamma radiation can recover the etch damage caused by F plasma treatment.
基金Project supported by the National Natural Science Foundation of China(Grant No.60736033)the Fundamental Research Funds for the Central Universities(Grant No.JY10000904009)
文摘This paper reports fluorine plasma treatment enhancement-mode HEMTs （high electronic mobility transistors） EHEMTs and conventional depletion-mode HEMTs DHEMTs fabricated on one wafer using separate litho-photography technology. It finds that fluorine plasma etches the AlGaN at a slow rate by capacitance-voltage measurement. Using capacitance-frequency measurement, it finds one type of trap in conventional DHEMTs with TT = （0.5 - 6） ms and DT ： （1 - 5）×10^13 cm^-2. eV^-1. Two types of trap are found in fluorine plasma treatment EHEMTs, fast with TW（f）= （0.2 - 2） μs and slow with TT（s） = （0.5 - 6） ms. The density of trap states evaluated on the EHEMTs is Dw（f） ： （1 - 3） × 10^12 cm^-2. eV^-1 and DT（s） =（2 - 6） × 10^12 cm-2. eV-1 for the fast and slow traps, respectively. The result shows that the fluorine plasma treatment reduces the slow trap density by about one order, but introduces a new type of fast trap. The slow trap is suggested to be a surface trap, related to the gate leakage current.
基金Project supported by the Major Program of the National Natural Science Foundation of China (Grant No. 50932002)
文摘The effects of ^60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electron- mobility transistors （E-mode HEMTs） are investigated. The results show that having been irradiated by^60Co γ-rays at a dose of 3 Mrad （Si）, the E-mode HEMT reduces its saturation drain current and maximal transconductance by 6% and 5%, respectively, and significantly increases both forward and reverse gate currents, while its threshold voltage is affected only slightly. The obvious performance degradation of E-mode A1GaN/GaN HEMTs is consistent with the creation of electronegative surface state charges in the source-gate spacer and gate-drain spacer after being irradiated.
基金Project supported by the National Postdoctoral Program for Innovative Talents,China(Grant No.BX201700184)the National Key Research and Development Program of China(Grant Nos.2016YFB0400105 and 2017YFB0403102)
文摘Pulsed metal organic chemical vapor deposition was employed to grow nearly polarization matched InAlGaN/GaN heterostructures. A relatively low sheet carrier density of 1.8×10^(12)cm^(-2), together with a high electron mobility of1229.5 cm^2/V·s, was obtained for the prepared heterostructures. The surface morphology of the heterostructures was also significantly improved, i.e., with a root mean square roughness of 0.29 nm in a 2 μm×2 μm scan area. In addition to the improved properties, the enhancement-mode metal–oxide–semiconductor high electron mobility transistors(MOSHEMTs) processed on the heterostructures not only exhibited a high threshold voltage(VTH) of 3.1 V, but also demonstrated a significantly enhanced drain output current density of 669 m A/mm. These values probably represent the largest values obtained from the InAlGaN based enhancement-mode devices to the best of our knowledge. This study strongly indicates that the InAlGaN/GaN heterostructures grown by pulsed metal organic chemical vapor deposition could be promising for the applications of novel nitride-based electronic devices.
基金Project supported by the National Key Research and Development Program of China(Grant No.2020YFB1804902)the National Natural Science Foundation of China(Grant No.61904135)+1 种基金the China Postdoctoral Science Foundation(Grant Nos.2018M640957 and BX20200262)the Natural Science Foundation of Shaanxi Province,China(Grant No.2020JQ-316).
文摘Ultra-thin barrier(UTB) 4-nm-Al Ga N/Ga N normally-off high electron mobility transistors(HEMTs) having a high current gain cut-off frequency( fT) are demonstrated by the stress-engineered compressive Si N trench technology.The compressive in-situ Si N guarantees the UTB-Al Ga N/Ga N heterostructure can operate a high electron density of1.27×1013 cm-2, a high uniform sheet resistance of 312.8 Ω/, but a negative threshold for the short-gate devices fabricated on it. With the lateral stress-engineering by full removing in-situ Si N in the 600-nm Si N trench, the short-gated(70 nm) devices obtain a threshold of 0.2 V, achieving the devices operating at enhancement-mode(E-mode). Meanwhile,the novel device also can operate a large current of 610 m A/mm and a high transconductance of 394 m S/mm for the Emode devices. Most of all, a high fT/fmax of 128 GHz/255 GHz is obtained, which is the highest value among the reported E-mode Al Ga N/Ga N HEMTs. Besides, being together with the 211 GHz/346 GHz of fT/fmax for the D-mode HEMTs fabricated on the same materials, this design of E/D-mode with the realization of fmax over 200 GHz in this work is the first one that can be used in Q-band mixed-signal application with further optimization. And the minimized processing difference between the E-and D-mode designs the addition of the Si N trench, will promise an enormous competitive advantage in the fabricating costs.
基金supported by the National Science and Technology Major Project,China(Grant No.2013ZX02308-002)the National Natural Science Foundation of China(Grant Nos.11435010,61474086,and 61404099)
文摘A novel groove-type channel enhancement-mode AlGaN/GaN MIS high electron mobility transistor（GTCE-HEMT）with a combined polar and nonpolar AlGaN/GaN heterostucture is presented. The device simulation shows a threshold voltage of 1.24 V, peak transconductance of 182 m S/mm, and subthreshold slope of 85 m V/dec, which are obtained by adjusting the device parameters. Interestingly, it is possible to control the threshold voltage accurately without precisely controlling the etching depth in fabrication by adopting this structure. Besides, the breakdown voltage（VB） is significantly increased by 78% in comparison with the value of the conventional MIS-HEMT. Moreover, the fabrication process of the novel device is entirely compatible with that of the conventional depletion-mode（D-mode） polar AlGaN/GaN HEMT. It presents a promising way to realize the switch application and the E/D-mode logic circuits.
基金supported by the Foundation of State Key Laboratory of Wide-Bandgap Semi-conductor Power Electronic Devices(No.2019KF001)National Natural Science Foundation of China(No.51677089)。
文摘When using traditional drive circuits,the enhancement-mode GaN(eGaN)HEMT will be affected by high switching speed characteristics and parasitic parameters leading to worse crosstalk problems.Currently,the existing crosstalk suppression drive circuits often have the disadvantages of increased switching loss,control complexity,and overall electromagnetic interference(EMI).Therefore,this paper combines the driving loop impedance control and the active Miller clamp method to propose an improved active Miller clamp drive circuit.First,the crosstalk mechanism is analyzed,and the crosstalk voltage model is established.Through the crosstalk voltage evaluation platform,the influencing factors are evaluated experimentally.Then,the operating principle of the improved active Miller clamp drive circuit is discussed,and the optimized parameter design method is given.Finally,the effect of the improved active Miller clamp method for suppressing crosstalk is experimentally verified.The crosstalk voltage was suppressed from 3.5 V and-3.5 V to 1 V and-1.3 V,respectively,by the improved circuit.
基金the National Natural Science Foundation of China(Grant Nos.61974111,11690042,and 61974115)the National Pre-research Foundation of China(Grant No.31512050402)the Fund of Innovation Center of Radiation Application,China(Grant No.KFZC2018040202).
文摘Two types of enhancement-mode(E-mode)AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors(MIS-HEMTs)with different gate insulators are fabricated on Si substrates.The HfO2 gate insulator and the Al2O3 gate insulator each with a thickness of 30 nm are grown by the plasma-enhanced atomic layer deposition(PEALD).The energy band diagrams of two types of dielectric MIS-HEMTs are compared.The breakdown voltage(VBR)of HfO2 dielectric layer and Al2O3 dielectric layer are 9.4 V and 15.9 V,respectively.With the same barrier thickness,the transconductance of MIS-HEMT with HfO2 is larger.The threshold voltage(Vth)of the HfO2 and Al2O3 MIS-HEMT are 2.0 V and 2.4 V,respectively,when the barrier layer thickness is 0 nm.The C-V characteristics are in good agreement with the Vth's transfer characteristics.As the barrier layer becomes thinner,the drain current density decreases sharply.Due to the dielectric/AlGaN interface is very close to the channel,the scattering of interface states will lead the electron mobility to decrease.The current collapse and the Ron of Al2O3 MIS-HEMT are smaller at the maximum gate voltage.As Al2O3 has excellent thermal stability and chemical stability,the interface state density of Al2O3/AlGaN is less than that of HfO2/AlGaN.
基金supported by the National Natural Science Foundation of China(Grant No.61334002)the Opening Project of Science and Technology on ReliabilityPhysics and Application Technology of Electronic Component Laboratory,China(Grant No.ZHD201206)
文摘A non-recessed-gate quasi-E-mode double heterojunction A1GaN/GaN high electron mobility transistor （quasi-E- DHEMT） with a thin barrier, high breakdown voltage and good performance of drain induced barrier lowering （DIBL） was presented. Due to the metal organic chemical vapor deposition （MOCVD） grown 9-nm undoped A1GaN barrier, the effect that the gate metal depleted the two-dimensiomal electron gas （2DEG） was greatly impressed. Therefore, the density of carriers in the channel was nearly zero. Hence, the threshold voltage was above 0 V. Quasi-E-DHEMT with 4.1%tm source-to-drain distance, 2.6-μm gate-to-drain distance, and 0.5-μm gate length showed a drain current of 260 mA/mm. The threshold voltage of this device was 0.165 V when the drain voltage was 10 V and the DIBL was 5.26 mV/V. The quasi-E-DHEMT drain leakage current at a drain voltage of 146 V and a gate voltage of -6 V was below 1 mA/mm. This indicated that the hard breakdown voltage was more than 146 V.
文摘In this paper,an interleaved LCLC converter with enhancement-mode(E-mode)GaN devices is introduced to achieve the accurate current sharing performance for data center applications. Any tolerance in the resonant tank elements can lead to large load imbalance between any two different phases. Due to the steep gain curves of LCLC converters,conventional current sharing methods are not effective. In the proposed converter,the impedances of the resonant networks are matched by switching a capacitor,i.e.,switch controlled capacitor(SCC),in series with the resonant capacitor in one or some of the phases,which results in accurate load current sharing among the phases with an accuracy around 0.025%. The load share of a phase is sensed through the resonant current on it,and the control logic applied to such current sharing can be achieved. By this method,accurate current sharing is achieved for a wide input voltage range required for the hold-up time in data center applications. Interleaving is applied in the proposed multiphase LCLC converter,resulting in low current stress on the output capacitor and allowing ceramic capacitor implementation. Moreover,phase shedding accomplishes high light load efficiency. The performance of the proposed interleaved LCLC converter is verified by a two-phase 1 k W prototype with an input voltage ranging from 250 V to 400 V and a fixed 12 V output voltage.
