We present an AlGaN/GaN high-electron mobility transistor（HEMT） device with both field plate（FP） and lowdensity drain（LDD）. The LDD is realized by the injection of negatively charged fluorine（F-） ions under lo...We present an AlGaN/GaN high-electron mobility transistor（HEMT） device with both field plate（FP） and lowdensity drain（LDD）. The LDD is realized by the injection of negatively charged fluorine（F-） ions under low power in the space between the gate and the drain electrodes. With a small-size FP and a LDD length equal to only 31% of the gate-drain spacing, the device effectively modifies the electric field distribution and achieves a breakdown voltage enhancement up to two times when compared with a device with only FP.展开更多
Frequency-dependent conductance measurements were carried out to investigate the trap states induced by reactive ion etching in A1GaN/GaN high-electron-mobility transistors （HEMTs） quantitatively. For the non-recess...Frequency-dependent conductance measurements were carried out to investigate the trap states induced by reactive ion etching in A1GaN/GaN high-electron-mobility transistors （HEMTs） quantitatively. For the non-recessed HEMT, the trap state density decreases from 2.48 × 1013 cm-2.eV-1 at an energy of 0.29 eV to 2.79 × 1012 cm-2.eV-1 at ET = 0.33 eV. In contrast, the trap state density of 2.38 × 1013-1.10× 1014 cm-2.eV-1 is located at ET in a range of 0.30-0.33 eV for the recessed HEMT. Thus, lots of trap states with shallow energy levels are induced by the gate recess etching. The induced shallow trap states can be changed into deep trap states by 350 ℃ annealing process. As a result, there are two different types of trap sates, fast and slow, in the annealed HEMT. The parameters of the annealed HEMT are ET = 0.29-0.31 eV and DT = 8.16× 1012-5.58 × 1013 cm-2.eV-1 for the fast trap states, and ET = 0.37-0.45 eV and DT = 1.84×1013- 8.50 × 1013 cm-2.eV-1 for the slow trap states. The gate leakage currents are changed by the etching and following annealing process, and this change can be explained by the analysis of the trap states.展开更多
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
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
Direct current（DC） reverse step voltage stress is applied on the gate of an AlGaN/GaN high-electron mobility transistor（HEMT）.Experiments show that parameters degenerate under stress.Large-signal parasitic source/...Direct current（DC） reverse step voltage stress is applied on the gate of an AlGaN/GaN high-electron mobility transistor（HEMT）.Experiments show that parameters degenerate under stress.Large-signal parasitic source/drain resistance（RS/RD） and gate-source forward I-V characteristics are recoverable after breakdown of the device under test（DUT）.Electrons trapped by both the AlGaN barrier trap and the surface state under stress lead to this phenomenon,and surface state recovery is the major reason for the recovery of device parameters.展开更多
In this paper, we present the combination of drain field plate （FP） and Schottky drain to improve the reverse blocking capability, and investigate the reverse blocking enhancement of drain FP in Schottky-drain AlGaN...In this paper, we present the combination of drain field plate （FP） and Schottky drain to improve the reverse blocking capability, and investigate the reverse blocking enhancement of drain FP in Schottky-drain AlGaN/GaN high-electron mobility transistors （HEMTs）. Drain FP and gate FP were employed in a two-dimensional simulation to improve the reverse blocking voltage （VRB） and the forward blocking voltage （VFB）. The drain-FP length, the gate-FP length and the passivation layer thickness were optimized. VRB and VFB were improved from -67 V and 134 V to -653 V and 868 V respectively after optimization. Simulation results suggest that the combination of drain FP and Schottky drain can enhance the reverse blocking capability significantly.展开更多
V-gate GaN high-electron-mobility transistors （HEMTs） are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si3N4 recess etching technology. Compared with standard ...V-gate GaN high-electron-mobility transistors （HEMTs） are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si3N4 recess etching technology. Compared with standard HEMTs, the fabricated V-gate HEMTs exhibit a 17% higher peak extrinsic transconductance due to a narrowed gate foot. Moreover, both the gate leakage and current dispersion are dramatically suppressed simultaneously, although a slight degradation of frequency response is observed. Based on a two-dimensional electric field simulation using Silvaco ＂ATLAS＂ for both standard HEMTs and V-gate HEMTs, the relaxation in peak electric field at the gate edge is identified as the predominant factor leading to the superior performance of V-gate HEMTs.展开更多
AlGaN/GaN high-electron-mobility transistors （HEMTs） with Al-doped ZnO （AZO） transparent gate electrodes are fabricated, and Ni/Au/Ni-gated HEMTs are produced in comparison. The AZO-gated HEMTs show good DC charac...AlGaN/GaN high-electron-mobility transistors （HEMTs） with Al-doped ZnO （AZO） transparent gate electrodes are fabricated, and Ni/Au/Ni-gated HEMTs are produced in comparison. The AZO-gated HEMTs show good DC characteristics and Schottky rectifying characteristics, and the gate electrodes achieve excellent transparencies. Compared with Ni/Au/Ni-gated HEMTs, AZO-gated HEMTs show a low saturation current, high threshold voltage, high Schottky barrier height, and low gate reverse leakage current. Due to the higher gate resistivity, AZO-gated HEMTs exhibit a current-gain cutoff frequency （fT） of 10 GHz and a power gain cutoff frequency （fmax） of 5 GHz, and lower maximum oscillation frequency than Ni/Au/Ni-gated HEMTs. Moreover, the C-V characteristics are measured and the gate interface characteristics of the AZO-gated devices are investigated by a C-V dual sweep.展开更多
The effects of gate length L_G on breakdown voltage VBRare investigated in AlGaN/GaN high-electron-mobility transistors（HEMTs） with L_G= 1 μm^20 μm. With the increase of L_G, VBRis first increased, and then satura...The effects of gate length L_G on breakdown voltage VBRare investigated in AlGaN/GaN high-electron-mobility transistors（HEMTs） with L_G= 1 μm^20 μm. With the increase of L_G, VBRis first increased, and then saturated at LG= 3 μm. For the HEMT with L_G= 1 μm, breakdown voltage VBRis 117 V, and it can be enhanced to 148 V for the HEMT with L-_G= 3 μm. The gate length of 3 μm can alleviate the buffer-leakage-induced impact ionization compared with the gate length of 1 μm, and the suppression of the impact ionization is the reason for improving the breakdown voltage.A similar suppression of the impact ionization exists in the HEMTs with LG〉 3 μm. As a result, there is no obvious difference in breakdown voltage among the HEMTs with LG= 3 μm^20 μm, and their breakdown voltages are in a range of 140 V–156 V.展开更多
In a grating-coupled high-electron-mobility transistor, weak terahertz emission with wavelength around 400um was observed by using a Fourier-transform spectrometer. The absolute terahertz emission power was extracted ...In a grating-coupled high-electron-mobility transistor, weak terahertz emission with wavelength around 400um was observed by using a Fourier-transform spectrometer. The absolute terahertz emission power was extracted from a strong background blackbody emission by using a modulation technique. The power of terahertz emission is proportional to the drain-source current, while the power of blackbody emission has a distinct relation with the electrical power. The dependence on the drain-source bias and the gate voltage suggests that the terahertz emission is induced by accelerated electrons interacting with the grating.展开更多
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.61334002)the Young Scientists Fund of the National Natural Science Foundation of China(Grant Nos.61404100 and 61106106)
文摘We present an AlGaN/GaN high-electron mobility transistor（HEMT） device with both field plate（FP） and lowdensity drain（LDD）. The LDD is realized by the injection of negatively charged fluorine（F-） ions under low power in the space between the gate and the drain electrodes. With a small-size FP and a LDD length equal to only 31% of the gate-drain spacing, the device effectively modifies the electric field distribution and achieves a breakdown voltage enhancement up to two times when compared with a device with only FP.
基金supported by the National Natural Science Foundation of China(Grant Nos.61334002 and 61106106)
文摘Frequency-dependent conductance measurements were carried out to investigate the trap states induced by reactive ion etching in A1GaN/GaN high-electron-mobility transistors （HEMTs） quantitatively. For the non-recessed HEMT, the trap state density decreases from 2.48 × 1013 cm-2.eV-1 at an energy of 0.29 eV to 2.79 × 1012 cm-2.eV-1 at ET = 0.33 eV. In contrast, the trap state density of 2.38 × 1013-1.10× 1014 cm-2.eV-1 is located at ET in a range of 0.30-0.33 eV for the recessed HEMT. Thus, lots of trap states with shallow energy levels are induced by the gate recess etching. The induced shallow trap states can be changed into deep trap states by 350 ℃ annealing process. As a result, there are two different types of trap sates, fast and slow, in the annealed HEMT. The parameters of the annealed HEMT are ET = 0.29-0.31 eV and DT = 8.16× 1012-5.58 × 1013 cm-2.eV-1 for the fast trap states, and ET = 0.37-0.45 eV and DT = 1.84×1013- 8.50 × 1013 cm-2.eV-1 for the slow trap states. The gate leakage currents are changed by the etching and following annealing process, and this change can be explained by the analysis of the trap states.
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 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 Key Science and Technology Foundation of Guangdong Province,China (Grant Nos. 2011A080801005 and 2010A080802001)the Guiding Project on the Integration of Industry,Education and Research of Guangdong Province,China (Grant No. 00802440123641045)the Strategic Emerging Industries,the Special Fund for LED Industry Projects of Guangdong Province,China (Grant No. 2012A080304003)
文摘Direct current（DC） reverse step voltage stress is applied on the gate of an AlGaN/GaN high-electron mobility transistor（HEMT）.Experiments show that parameters degenerate under stress.Large-signal parasitic source/drain resistance（RS/RD） and gate-source forward I-V characteristics are recoverable after breakdown of the device under test（DUT）.Electrons trapped by both the AlGaN barrier trap and the surface state under stress lead to this phenomenon,and surface state recovery is the major reason for the recovery of device parameters.
基金supported by the National Natural Science Foundation of China(Grant Nos.61334002 and 61106106)the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory,China(Grant No.ZHD201206)
文摘In this paper, we present the combination of drain field plate （FP） and Schottky drain to improve the reverse blocking capability, and investigate the reverse blocking enhancement of drain FP in Schottky-drain AlGaN/GaN high-electron mobility transistors （HEMTs）. Drain FP and gate FP were employed in a two-dimensional simulation to improve the reverse blocking voltage （VRB） and the forward blocking voltage （VFB）. The drain-FP length, the gate-FP length and the passivation layer thickness were optimized. VRB and VFB were improved from -67 V and 134 V to -653 V and 868 V respectively after optimization. Simulation results suggest that the combination of drain FP and Schottky drain can enhance the reverse blocking capability significantly.
基金Project supported by the Program for New Century Excellent Talents in University, China (Grant No. NCET-12-0915)the National Natural Science Foundation of China (Grant Nos. 61106106 and 61204085)
文摘V-gate GaN high-electron-mobility transistors （HEMTs） are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si3N4 recess etching technology. Compared with standard HEMTs, the fabricated V-gate HEMTs exhibit a 17% higher peak extrinsic transconductance due to a narrowed gate foot. Moreover, both the gate leakage and current dispersion are dramatically suppressed simultaneously, although a slight degradation of frequency response is observed. Based on a two-dimensional electric field simulation using Silvaco ＂ATLAS＂ for both standard HEMTs and V-gate HEMTs, the relaxation in peak electric field at the gate edge is identified as the predominant factor leading to the superior performance of V-gate HEMTs.
基金supported by the National Key Science & Technology Special Project (Grant No. 2008ZX01002-002)the National Natural Science Foundation of China (Grant No. 61106106)the Fundamental Research Funds for the Central Universities,China (Grant Nos. K50510250003 and K50510250006)
文摘AlGaN/GaN high-electron-mobility transistors （HEMTs） with Al-doped ZnO （AZO） transparent gate electrodes are fabricated, and Ni/Au/Ni-gated HEMTs are produced in comparison. The AZO-gated HEMTs show good DC characteristics and Schottky rectifying characteristics, and the gate electrodes achieve excellent transparencies. Compared with Ni/Au/Ni-gated HEMTs, AZO-gated HEMTs show a low saturation current, high threshold voltage, high Schottky barrier height, and low gate reverse leakage current. Due to the higher gate resistivity, AZO-gated HEMTs exhibit a current-gain cutoff frequency （fT） of 10 GHz and a power gain cutoff frequency （fmax） of 5 GHz, and lower maximum oscillation frequency than Ni/Au/Ni-gated HEMTs. Moreover, the C-V characteristics are measured and the gate interface characteristics of the AZO-gated devices are investigated by a C-V dual sweep.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61334002,61106106,and 61204085)
文摘The effects of gate length L_G on breakdown voltage VBRare investigated in AlGaN/GaN high-electron-mobility transistors（HEMTs） with L_G= 1 μm^20 μm. With the increase of L_G, VBRis first increased, and then saturated at LG= 3 μm. For the HEMT with L_G= 1 μm, breakdown voltage VBRis 117 V, and it can be enhanced to 148 V for the HEMT with L-_G= 3 μm. The gate length of 3 μm can alleviate the buffer-leakage-induced impact ionization compared with the gate length of 1 μm, and the suppression of the impact ionization is the reason for improving the breakdown voltage.A similar suppression of the impact ionization exists in the HEMTs with LG〉 3 μm. As a result, there is no obvious difference in breakdown voltage among the HEMTs with LG= 3 μm^20 μm, and their breakdown voltages are in a range of 140 V–156 V.
基金Project supported by the National Basic Research Program of China(No.G2009CB929303)the Knowledge Innovation Program of the Chinese Academy of Sciences(No.Y0BAQ31001)the National Natural Science Foundation of China(No.60871077)
文摘In a grating-coupled high-electron-mobility transistor, weak terahertz emission with wavelength around 400um was observed by using a Fourier-transform spectrometer. The absolute terahertz emission power was extracted from a strong background blackbody emission by using a modulation technique. The power of terahertz emission is proportional to the drain-source current, while the power of blackbody emission has a distinct relation with the electrical power. The dependence on the drain-source bias and the gate voltage suggests that the terahertz emission is induced by accelerated electrons interacting with the grating.
