Nonalloyed ohmic contacts regrown by metal-organic chemical vapor deposition are performed on AlGaN/GaN high-electron-mobility transistors. Low ohmic contact resistance of 0.15Ω.mm is obtained. It is found that the s...Nonalloyed ohmic contacts regrown by metal-organic chemical vapor deposition are performed on AlGaN/GaN high-electron-mobility transistors. Low ohmic contact resistance of 0.15Ω.mm is obtained. It is found that the sidewall obliquity near the regrown interface induced by the plasma dry etching has great influence on the total contact resistance. The fabricated device with a 100-nm T-shaped gate demonstrates a maximum drain current density of 0.95 A/mm at Vgs = 1 V and a maximum peak extrinsic transcondutance Gm of 216mS/ram. Moreover, a current gain cut-off frequency fT of 115 GHz and a maximum oscillation frequency fmax of 127 GHz are achieved.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
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
A novel normally-off AlGaN/GaN high-electron-mobility transistor(HEMT)with a p-GaN Schottky hybrid gate(PSHG)is proposed,and compared with the conventional p-GaN normally-off AlGaN/GaN HEMTs.This structure can be real...A novel normally-off AlGaN/GaN high-electron-mobility transistor(HEMT)with a p-GaN Schottky hybrid gate(PSHG)is proposed,and compared with the conventional p-GaN normally-off AlGaN/GaN HEMTs.This structure can be realized by selective etching of p-GaN layer,which enables the Schottky junction and PN junction to control the channel charge at the same time.The direct current(DC)and switching characteristics of the PSHG HEMTs are simulated by Slivaco TCAD,and the p-GaN HEMTs and conventional normally-on HEMTs are also simulated for comparison.The simulation results show that the PSHG HEMTs have a higher current density and a lower on-resistance than p-GaN HEMTs,which is more obvious with the decrease of p-GaN ratios of the PSHG HEMTs.The breakdown voltage and threshold voltage of the PSHG HEMTs are very close to those of the p-GaN HEMTs.In addition,the PSHG HEMTs have a higher switching speed than the conventional normally-on HEMTs,and the p-GaN layer ratio has no obvious effect on the switching speed.展开更多
Superior characteristics of Al Ga N-channel metal-insulator-semiconductor（MIS） high electron mobility transistors（HEMTs） at high temperatures are demonstrated in detail. The temperature coefficient of the maximum ...Superior characteristics of Al Ga N-channel metal-insulator-semiconductor（MIS） high electron mobility transistors（HEMTs） at high temperatures are demonstrated in detail. The temperature coefficient of the maximum saturation drain current for the Al GaN-channel MIS HEMT can be reduced by 50% compared with the Ga N-channel HEMT. Moreover, benefiting from the better suppression of gate current and reduced leakage current in the buffer layer, the Al Ga N-channel MIS HEMT demonstrates an average breakdown electric field of 1.83 MV/cm at25℃ and 1.06 MV/cm at 300℃, which is almost 2 times and 3 times respectively larger than that of the reference Ga N-channel HEMT. Pulsed mode analyses suggest that the proposed device suffers from smaller current collapse when the temperature reaches as high as 300℃.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
The capacitance-voltage characteristics of AIGaN/GaN high-electron-mobility transistors （HEMTS） are measured in the temperature range of 223-398K. The dependence of capacitance on frequency at various temperatures i...The capacitance-voltage characteristics of AIGaN/GaN high-electron-mobility transistors （HEMTS） are measured in the temperature range of 223-398K. The dependence of capacitance on frequency at various temperatures is analyzed. At lower temperatures, the capacitance decreases only very slightly with frequency. At higher frequencies the curves for all temperatures tend to one capacitance value. Such behavior can be attributed to the interface states or the dislocations.展开更多
In this work,we investigate the impact of the whole small recess offset on DC and RF characteristics of InP high electron mobility transistors(HEMTs).L_(g)=80 nm HEMTs are fabricated with a double-recessed gate proces...In this work,we investigate the impact of the whole small recess offset on DC and RF characteristics of InP high electron mobility transistors(HEMTs).L_(g)=80 nm HEMTs are fabricated with a double-recessed gate process.We focus on their DC and RF responses,including the maximum transconductance(g_(m_max)),ON-resistance(R_(ON)),current-gain cutoff frequency(f_(T)),and maximum oscillation frequency(f_(max)).The devices have almost same RON.The g_(m_max) improves as the whole small recess moves toward the source.However,a small gate to source capacitance(C_(gs))and a small drain output conductance(g_(ds))lead to the largest f_(T),although the whole small gate recess moves toward the drain leads to the smaller g_(m_max).According to the small-signal modeling,the device with the whole small recess toward drain exhibits an excellent RF characteristics,such as f_(T)=372 GHz and f_(max)=394 GHz.This result is achieved by paying attention to adjust resistive and capacitive parasitics,which play a key role in high-frequency response.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
An accurate and novel small-signal equivalent circuit model for GaN high-electron-mobility transistors(HEMTs)is proposed,which considers a dual-field-plate(FP)made up of a gate-FP and a source-FP.The equivalent circui...An accurate and novel small-signal equivalent circuit model for GaN high-electron-mobility transistors(HEMTs)is proposed,which considers a dual-field-plate(FP)made up of a gate-FP and a source-FP.The equivalent circuit of the overall model is composed of parasitic elements,intrinsic transistors,gate-FP,and source-FP networks.The equivalent circuit of the gate-FP is identical to that of the intrinsic transistor.In order to simplify the complexity of the model,a series combination of a resistor and a capacitor is employed to represent the source-FP.The analytical extraction procedure of the model parameters is presented based on the proposed equivalent circuit.The verification is carried out on a 4×250μm GaN HEMT device with a gate-FP and a source-FP in a 0.45μm technology.Compared with the classic model,the proposed novel small-signal model shows closer agreement with measured S-parameters in the range of 1.0 to 18.0 GHz.展开更多
In this paper, we present a high-efficiency S-band gallium nitride （GaN） power amplifier （PA）. This amplifier is fabri- cated based on a self-developed GaN high-electron-mobility transistor （HEMT） with 10 mm gat...In this paper, we present a high-efficiency S-band gallium nitride （GaN） power amplifier （PA）. This amplifier is fabri- cated based on a self-developed GaN high-electron-mobility transistor （HEMT） with 10 mm gate width on SiC substrate. Harmonic manipulation circuits are presented in the amplifier. The matching networks consist of microstrip lines and discrete components. Open-circuited stub lines in both input and output are used to tune the 2rid harmonic wave and match the GaN HEMT to the highest efficiency condition. The developed amplifier delivers an output power of 48.5 dBm （70 W） with a power-added efficiency （PAE） of 72.2% at 2 GHz in pulse condition. When operating at 1.8-2.2 GHz （20% relative bandwidth）, the amplifier provides an output power higher than 48 dBm （,-~ 65 W）, with a PAE over 70% and a power gain above 15 dB. When operating in continuous-wave （CW） operating conditions, the amplifier gives an output power over 46 dBm （40 W） with PAE beyond 60% over the whole operation frequency range.展开更多
We investigate the negative transconductance effect in p-GaN gate AlGaN/GaN high-electron-mobility transistor(HEMT) associated with traps in the unintentionally doped GaN buffer layer. We find that a negative transcon...We investigate the negative transconductance effect in p-GaN gate AlGaN/GaN high-electron-mobility transistor(HEMT) associated with traps in the unintentionally doped GaN buffer layer. We find that a negative transconductance effect occurs with increasing the trap concentration and capture cross section when calculating transfer characteristics.The electron tunneling through AlGaN barrier and the reduced electric field discrepancy between drain side and gate side induced by traps are reasonably explained by analyzing the band diagrams, output characteristics, and the electric field strength of the channel of the devices under different trap concentrations and capture cross sections.展开更多
The N_(2)O radicals in-situ treatment on gate region has been employed to improve device performance of recessedgate Al Ga N/Ga N high-electron-mobility transistors(HEMTs).The samples after gate recess etching were tr...The N_(2)O radicals in-situ treatment on gate region has been employed to improve device performance of recessedgate Al Ga N/Ga N high-electron-mobility transistors(HEMTs).The samples after gate recess etching were treated by N_(2)O radicals without physical bombardment.After in-situ treatment(IST)processing,the gate leakage currents decreased by more than one order of magnitude compared to the sample without IST.The fabricated HEMTs with the IST process show a low reverse gate current of 10;A/mm,high on/off current ratio of 108,and high f_(T)×L_(g)of 13.44 GHz·μm.A transmission electron microscope(TEM)imaging illustrates an oxide layer with a thickness of 1.8 nm exists at the AlGaN surface.X-ray photoelectron spectroscopy(XPS)measurement shows that the content of the Al-O and Ga-O bonds elevated after IST,indicating that the Al-N and Ga-N bonds on the AlGaN surface were broken and meanwhile the Al-O and Ga-O bonds formed.The oxide formed by a chemical reaction between radicals and the surface of the AlGaN barrier layer is responsible for improved device characteristics.展开更多
A self-supporting T-shaped gate(SST-gate) GaN device and process method using electron beam lithography are proposed.An AlGaN/GaN high-electron-mobility transistor(HEMT) device with a gate length of 100 nm is fabricat...A self-supporting T-shaped gate(SST-gate) GaN device and process method using electron beam lithography are proposed.An AlGaN/GaN high-electron-mobility transistor(HEMT) device with a gate length of 100 nm is fabricated by this method.The current gain cutoff frequency(f_(T)) is 60 GHz,and the maximum oscillation frequency(f_(max)) is 104 GHz.The current collapse has improved by 13% at static bias of(V_(GSQ),V_(DSQ))=(-8 V,10 V),and gate manufacturing yield has improved by 17% compared with the traditional floating T-shaped gate(FT-gate) device.展开更多
The degradation mechanisms of enhancement-mode p-GaN gate AlGaN/GaN high-electron mobility transistor was analyzed extensively,by means of drain voltage stress and gate bias stress.The results indicate that:(ⅰ) High ...The degradation mechanisms of enhancement-mode p-GaN gate AlGaN/GaN high-electron mobility transistor was analyzed extensively,by means of drain voltage stress and gate bias stress.The results indicate that:(ⅰ) High constant drain voltage stress has only a negligible impact on the device electrical parameters,with a slightly first increase and then decrease in output current;(ⅱ) A negative shift of threshold voltage and increased output current were observed in the device subjected to forward gate bias stress,which is mainly ascribed to the hole-trapping induced by high electric field across the p-GaN/AlGaN interface;(ⅲ) The analyzed device showed an excellent behavior at reverse gate bias stress,with almost unaltered threshold voltage,output current,and gate leakage current,exhibiting a large gate swing in the negative direction.The results are meaningful and valuable in directing the process optimization towards a high voltage and high reliable enhanced AlGaN/GaN high-electron mobility transistor.展开更多
This article presents the design and performance of a single-pole double-throw(SPDT)switch operating in 50-110 GHz.The switch is fabricated in a 100-nm GaN high-electron-mobility transistors(HEMT)technology.To realize...This article presents the design and performance of a single-pole double-throw(SPDT)switch operating in 50-110 GHz.The switch is fabricated in a 100-nm GaN high-electron-mobility transistors(HEMT)technology.To realize high-power capability,the dimensions of GaN HEMTs are selected by simulation verification.To enhance the isolation,an improved structure of shunt HEMT with two ground holes is employed.To extend the operation bandwidth,the SPDT switch with multi-section resonant units is proposed and analyzed.To verify the SPDT switch design,a prototype operating in 50-110 GHz is fabricated.The measured results show that the fabricated SPDT switch monolithic microwave integrated circuit(MMIC)achieves an input 1 dB compression point(P_(1dB))of 38 dBm at 94 GHz,and isolation within the range of 33 dB to 54 dB in 50-110 GHz.The insertion loss of the switch is less than 2.1 dB,while the voltage standing wave ratios(VSWR)of the input port and output port are both less than 1.8 in the operation bandwidth.Based on the measured results,the presented SPDT switch MMIC demonstrates high power capability and high isolation compared with other reported millimeter-wave SPDT MMIC designs.展开更多
lnA1N/GaN high-electron-mobility transistors （HEMTs） on SiC substrate were fabricated and character- ized. Several techniques, consisting of high electron density, 70 nm T-shaped gate, low ohmic contacts and a short...lnA1N/GaN high-electron-mobility transistors （HEMTs） on SiC substrate were fabricated and character- ized. Several techniques, consisting of high electron density, 70 nm T-shaped gate, low ohmic contacts and a short drain-source distance, are integrated to gain high device performance. The fabricated InA1N/GaN HEMTs exhibit a maximum drain saturation current density of 1.65 A/ram at Vgs = 1 V and a maximum peak transconductance of 382 mS/rnm. In addition, a unity current gain cut-off frequency （fT） of 162 GHz and a maximum oscillation frequency （fmax） of 176 GHz are achieved on the devices with the 70 nm gate length.展开更多
A novel AlGaN/GaN high electric mobility transistor（HEMT） with polyimide（PI）/chromium（Cr） as thepassivationlayerisproposedforenhancingbreakdownvoltageanditsDCperformanceisalsoinvestigated.The Cr nanoparticles fi...A novel AlGaN/GaN high electric mobility transistor（HEMT） with polyimide（PI）/chromium（Cr） as thepassivationlayerisproposedforenhancingbreakdownvoltageanditsDCperformanceisalsoinvestigated.The Cr nanoparticles firstly introduced in PI thin films by the co-evaporation can be used to increase the permittivity of PI film. The high-permittivity PI/Cr passivation acting as field plate can suppress the fringing electric field peak at the drain-side edge of the gate electrode. This mechanism is demonstrated in accord with measured results. The experimental results show that in comparison with the AlGaN/GaN HEMTs without passivation, the breakdown voltage of HEMTs with the PI/Cr composite thin films can be significantly improved, from 122 to 248 V.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 61306113
文摘Nonalloyed ohmic contacts regrown by metal-organic chemical vapor deposition are performed on AlGaN/GaN high-electron-mobility transistors. Low ohmic contact resistance of 0.15Ω.mm is obtained. It is found that the sidewall obliquity near the regrown interface induced by the plasma dry etching has great influence on the total contact resistance. The fabricated device with a 100-nm T-shaped gate demonstrates a maximum drain current density of 0.95 A/mm at Vgs = 1 V and a maximum peak extrinsic transcondutance Gm of 216mS/ram. Moreover, a current gain cut-off frequency fT of 115 GHz and a maximum oscillation frequency fmax of 127 GHz are achieved.
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 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supported by the National Natural Science Foundation of China(Grant No.62004150)Postdoctoral Science Foundation of China(Grant No.2018M643575)the Fundamental Research Funds for the Central Universities,and the Innovation Fund of Xidian University(Grant No.JB211104)。
文摘A novel normally-off AlGaN/GaN high-electron-mobility transistor(HEMT)with a p-GaN Schottky hybrid gate(PSHG)is proposed,and compared with the conventional p-GaN normally-off AlGaN/GaN HEMTs.This structure can be realized by selective etching of p-GaN layer,which enables the Schottky junction and PN junction to control the channel charge at the same time.The direct current(DC)and switching characteristics of the PSHG HEMTs are simulated by Slivaco TCAD,and the p-GaN HEMTs and conventional normally-on HEMTs are also simulated for comparison.The simulation results show that the PSHG HEMTs have a higher current density and a lower on-resistance than p-GaN HEMTs,which is more obvious with the decrease of p-GaN ratios of the PSHG HEMTs.The breakdown voltage and threshold voltage of the PSHG HEMTs are very close to those of the p-GaN HEMTs.In addition,the PSHG HEMTs have a higher switching speed than the conventional normally-on HEMTs,and the p-GaN layer ratio has no obvious effect on the switching speed.
文摘Superior characteristics of Al Ga N-channel metal-insulator-semiconductor（MIS） high electron mobility transistors（HEMTs） at high temperatures are demonstrated in detail. The temperature coefficient of the maximum saturation drain current for the Al GaN-channel MIS HEMT can be reduced by 50% compared with the Ga N-channel HEMT. Moreover, benefiting from the better suppression of gate current and reduced leakage current in the buffer layer, the Al Ga N-channel MIS HEMT demonstrates an average breakdown electric field of 1.83 MV/cm at25℃ and 1.06 MV/cm at 300℃, which is almost 2 times and 3 times respectively larger than that of the reference Ga N-channel HEMT. Pulsed mode analyses suggest that the proposed device suffers from smaller current collapse when the temperature reaches as high as 300℃.
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Supported by the National Natural Science Foundation of China under Grant Nos 60976059 and 61106074the National Basic Research Program of China under Grant No 2011CB301704
文摘The capacitance-voltage characteristics of AIGaN/GaN high-electron-mobility transistors （HEMTS） are measured in the temperature range of 223-398K. The dependence of capacitance on frequency at various temperatures is analyzed. At lower temperatures, the capacitance decreases only very slightly with frequency. At higher frequencies the curves for all temperatures tend to one capacitance value. Such behavior can be attributed to the interface states or the dislocations.
基金Supported by the Terahertz Multi User RF Transceiver System Development Project(Z211100004421012).
文摘In this work,we investigate the impact of the whole small recess offset on DC and RF characteristics of InP high electron mobility transistors(HEMTs).L_(g)=80 nm HEMTs are fabricated with a double-recessed gate process.We focus on their DC and RF responses,including the maximum transconductance(g_(m_max)),ON-resistance(R_(ON)),current-gain cutoff frequency(f_(T)),and maximum oscillation frequency(f_(max)).The devices have almost same RON.The g_(m_max) improves as the whole small recess moves toward the source.However,a small gate to source capacitance(C_(gs))and a small drain output conductance(g_(ds))lead to the largest f_(T),although the whole small gate recess moves toward the drain leads to the smaller g_(m_max).According to the small-signal modeling,the device with the whole small recess toward drain exhibits an excellent RF characteristics,such as f_(T)=372 GHz and f_(max)=394 GHz.This result is achieved by paying attention to adjust resistive and capacitive parasitics,which play a key role in high-frequency response.
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.
文摘An accurate and novel small-signal equivalent circuit model for GaN high-electron-mobility transistors(HEMTs)is proposed,which considers a dual-field-plate(FP)made up of a gate-FP and a source-FP.The equivalent circuit of the overall model is composed of parasitic elements,intrinsic transistors,gate-FP,and source-FP networks.The equivalent circuit of the gate-FP is identical to that of the intrinsic transistor.In order to simplify the complexity of the model,a series combination of a resistor and a capacitor is employed to represent the source-FP.The analytical extraction procedure of the model parameters is presented based on the proposed equivalent circuit.The verification is carried out on a 4×250μm GaN HEMT device with a gate-FP and a source-FP in a 0.45μm technology.Compared with the classic model,the proposed novel small-signal model shows closer agreement with measured S-parameters in the range of 1.0 to 18.0 GHz.
基金Project supported by the National Natural Science Foundation of China(Grant No.61203211)the Natural Science Foundation of Jiangsu Higher Education Institutions of China(Grant No.13KJB140006)the Foundation for Outstanding Young Teachers of Nanjing University of Information Science&Technology,China(Grant No.20110423)
文摘In this paper, we present a high-efficiency S-band gallium nitride （GaN） power amplifier （PA）. This amplifier is fabri- cated based on a self-developed GaN high-electron-mobility transistor （HEMT） with 10 mm gate width on SiC substrate. Harmonic manipulation circuits are presented in the amplifier. The matching networks consist of microstrip lines and discrete components. Open-circuited stub lines in both input and output are used to tune the 2rid harmonic wave and match the GaN HEMT to the highest efficiency condition. The developed amplifier delivers an output power of 48.5 dBm （70 W） with a power-added efficiency （PAE） of 72.2% at 2 GHz in pulse condition. When operating at 1.8-2.2 GHz （20% relative bandwidth）, the amplifier provides an output power higher than 48 dBm （,-~ 65 W）, with a PAE over 70% and a power gain above 15 dB. When operating in continuous-wave （CW） operating conditions, the amplifier gives an output power over 46 dBm （40 W） with PAE beyond 60% over the whole operation frequency range.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0402900)the National Natural Science Foundation of China(Grant No.61634002)+1 种基金the Scientific Research Foundation of Graduate School of Nanjing University,China(Grant No.2016CL03)the Key Project of Jiangsu Province,China(Grant No.BE2016174)
文摘We investigate the negative transconductance effect in p-GaN gate AlGaN/GaN high-electron-mobility transistor(HEMT) associated with traps in the unintentionally doped GaN buffer layer. We find that a negative transconductance effect occurs with increasing the trap concentration and capture cross section when calculating transfer characteristics.The electron tunneling through AlGaN barrier and the reduced electric field discrepancy between drain side and gate side induced by traps are reasonably explained by analyzing the band diagrams, output characteristics, and the electric field strength of the channel of the devices under different trap concentrations and capture cross sections.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB1802100)the National Natural Science Foundation of China(Grant Nos.62104184,62090014,62104178,and 62104179)+1 种基金the Fundamental Research Funds for the Central Universities of China(Grant Nos.XJS201102,XJS211101,XJS211106,and ZDRC2002)the Natural Science Foundation of Shaanxi Province,China(Grant Nos.2020JM-191 and 2018HJCG-20)。
文摘The N_(2)O radicals in-situ treatment on gate region has been employed to improve device performance of recessedgate Al Ga N/Ga N high-electron-mobility transistors(HEMTs).The samples after gate recess etching were treated by N_(2)O radicals without physical bombardment.After in-situ treatment(IST)processing,the gate leakage currents decreased by more than one order of magnitude compared to the sample without IST.The fabricated HEMTs with the IST process show a low reverse gate current of 10;A/mm,high on/off current ratio of 108,and high f_(T)×L_(g)of 13.44 GHz·μm.A transmission electron microscope(TEM)imaging illustrates an oxide layer with a thickness of 1.8 nm exists at the AlGaN surface.X-ray photoelectron spectroscopy(XPS)measurement shows that the content of the Al-O and Ga-O bonds elevated after IST,indicating that the Al-N and Ga-N bonds on the AlGaN surface were broken and meanwhile the Al-O and Ga-O bonds formed.The oxide formed by a chemical reaction between radicals and the surface of the AlGaN barrier layer is responsible for improved device characteristics.
基金Project supported by the National Natural Science Foundation of China(Grant No.62188102)the Natural Science Basic Research Program of Shaanxi Province,China(Grant No.2022JM-316)the Fund from the Ministry of Education of China(Grant No.8091B042112)。
文摘A self-supporting T-shaped gate(SST-gate) GaN device and process method using electron beam lithography are proposed.An AlGaN/GaN high-electron-mobility transistor(HEMT) device with a gate length of 100 nm is fabricated by this method.The current gain cutoff frequency(f_(T)) is 60 GHz,and the maximum oscillation frequency(f_(max)) is 104 GHz.The current collapse has improved by 13% at static bias of(V_(GSQ),V_(DSQ))=(-8 V,10 V),and gate manufacturing yield has improved by 17% compared with the traditional floating T-shaped gate(FT-gate) device.
基金Project supported by the Equipment Developing Advanced Research Program of China(Grant No.6140A24030107)。
文摘The degradation mechanisms of enhancement-mode p-GaN gate AlGaN/GaN high-electron mobility transistor was analyzed extensively,by means of drain voltage stress and gate bias stress.The results indicate that:(ⅰ) High constant drain voltage stress has only a negligible impact on the device electrical parameters,with a slightly first increase and then decrease in output current;(ⅱ) A negative shift of threshold voltage and increased output current were observed in the device subjected to forward gate bias stress,which is mainly ascribed to the hole-trapping induced by high electric field across the p-GaN/AlGaN interface;(ⅲ) The analyzed device showed an excellent behavior at reverse gate bias stress,with almost unaltered threshold voltage,output current,and gate leakage current,exhibiting a large gate swing in the negative direction.The results are meaningful and valuable in directing the process optimization towards a high voltage and high reliable enhanced AlGaN/GaN high-electron mobility transistor.
文摘This article presents the design and performance of a single-pole double-throw(SPDT)switch operating in 50-110 GHz.The switch is fabricated in a 100-nm GaN high-electron-mobility transistors(HEMT)technology.To realize high-power capability,the dimensions of GaN HEMTs are selected by simulation verification.To enhance the isolation,an improved structure of shunt HEMT with two ground holes is employed.To extend the operation bandwidth,the SPDT switch with multi-section resonant units is proposed and analyzed.To verify the SPDT switch design,a prototype operating in 50-110 GHz is fabricated.The measured results show that the fabricated SPDT switch monolithic microwave integrated circuit(MMIC)achieves an input 1 dB compression point(P_(1dB))of 38 dBm at 94 GHz,and isolation within the range of 33 dB to 54 dB in 50-110 GHz.The insertion loss of the switch is less than 2.1 dB,while the voltage standing wave ratios(VSWR)of the input port and output port are both less than 1.8 in the operation bandwidth.Based on the measured results,the presented SPDT switch MMIC demonstrates high power capability and high isolation compared with other reported millimeter-wave SPDT MMIC designs.
基金supported by the National Natural Science Foundation of China(No.61306113)
文摘lnA1N/GaN high-electron-mobility transistors （HEMTs） on SiC substrate were fabricated and character- ized. Several techniques, consisting of high electron density, 70 nm T-shaped gate, low ohmic contacts and a short drain-source distance, are integrated to gain high device performance. The fabricated InA1N/GaN HEMTs exhibit a maximum drain saturation current density of 1.65 A/ram at Vgs = 1 V and a maximum peak transconductance of 382 mS/rnm. In addition, a unity current gain cut-off frequency （fT） of 162 GHz and a maximum oscillation frequency （fmax） of 176 GHz are achieved on the devices with the 70 nm gate length.
基金Project supported by the National Natural Science Foundation of China(No.50932002)the Research Foundation for the DoctoralProgram of Higher Education of China(No.2012018530003)
文摘A novel AlGaN/GaN high electric mobility transistor（HEMT） with polyimide（PI）/chromium（Cr） as thepassivationlayerisproposedforenhancingbreakdownvoltageanditsDCperformanceisalsoinvestigated.The Cr nanoparticles firstly introduced in PI thin films by the co-evaporation can be used to increase the permittivity of PI film. The high-permittivity PI/Cr passivation acting as field plate can suppress the fringing electric field peak at the drain-side edge of the gate electrode. This mechanism is demonstrated in accord with measured results. The experimental results show that in comparison with the AlGaN/GaN HEMTs without passivation, the breakdown voltage of HEMTs with the PI/Cr composite thin films can be significantly improved, from 122 to 248 V.
