AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degrad...AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current IDsat, maximal transconductance gm, and the positive shift of threshold voltage VTH at high drain-source voltage VDS. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEC depletion a little during the high-electric-field stress. After the hot carrier stress with VDS = 20 V and VGS= 0 V applied to the device for 104 sec, the SiN passivation decreases the stress-induced degradation of IDsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of IDsat, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted.展开更多
In this paper we present a novel approach to modeling AlGaN/GaN high electron mobility transistor (HEMT) with an artificial neural network (ANN). The AlGaN/GaN HEMT device structure and its fabrication process are...In this paper we present a novel approach to modeling AlGaN/GaN high electron mobility transistor (HEMT) with an artificial neural network (ANN). The AlGaN/GaN HEMT device structure and its fabrication process are described. The circuit-based Neuro-space mapping (neuro-SM) technique is studied in detail. The EEHEMT model is implemented according to the measurement results of the designed device, which serves as a coarse model. An ANN is proposed to model AIGaN/CaN HEMT based on the coarse model. Its optimization is performed. The simulation results from the model are compared with the measurement results. It is shown that the simulation results obtained from the ANN model of A1GaN/GaN HEMT are more accurate than those obtained from the EEHEMT model.展开更多
In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized,...In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized, and breakdown voltage VBR is saturated at 1085 V for gate–drain spacing LGD ≥ 8 μm. On the basis of the HEMT with a gate FP, a drain FP is added with LGD=10 μm. For the length of the drain FP LDF ≤ 2 μm, VBR is almost kept at 1085 V, showing no degradation. When LDF exceeds 2 μm, VBR decreases obviously as LDF increases. Moreover, the larger the LDF, the larger the decrease of VBR. It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the LGD at which VBR begins to saturate in the first structure. The electric field and potential distribution are simulated and analyzed to account for the decrease of VBR.展开更多
A novel A1GaN/GaN high electron mobility transistor (HEMT) with double buried p-type layers (DBPLs) in the GaN buffer layer and its mechanism are studied. The DBPL A1GaN/GaN HEMT is characterized by two equi-long ...A novel A1GaN/GaN high electron mobility transistor (HEMT) with double buried p-type layers (DBPLs) in the GaN buffer layer and its mechanism are studied. The DBPL A1GaN/GaN HEMT is characterized by two equi-long p-type GaN layers which are buried in the GaN buffer layer under the source side. Under the condition of high-voltage blocking state, two reverse p-n junctions introduced by the buried p-type layers will effectively modulate the surface and bulk electric fields. Meanwhile, the buffer leakage is well suppressed in this structure and both lead to a high breakdown voltage. The simulations show that the breakdown voltage of the DBPL structure can reach above 2000 V from 467 V of the conventional structure with the same gate-drain length of 8μm.展开更多
A1GaN/GaN high electron mobility transistors (HEMTs) were exposed to 1 MeV neutron irradiation at a neutron ftuence of 1 × 10^15 cm-2. The dc characteristics of the devices, such as the drain saturation current...A1GaN/GaN high electron mobility transistors (HEMTs) were exposed to 1 MeV neutron irradiation at a neutron ftuence of 1 × 10^15 cm-2. The dc characteristics of the devices, such as the drain saturation current and the maximum transconductance, decreased after neutron irradiation. The gate leakage currents increased obviously after neutron irradiation. However, the rf characteristics, such as the cut-off frequency and the maximum frequency, were hardly affected by neutron irradiation. The A1GaN/GaN heterojunctions have been employed for the better understanding of the degradation mechanism. It is shown in the Hall measurements and capacitance voltage tests that the mobility and concentration of two-dimensional electron gas (2DEG) decreased after neutron irradiation. Tbere was no evidence of the full-width at half-maximum of X-ray diffraction (XRD) rocking curve changing after irradiation, so the dislocation was not influenced by neutron irradiation. It is concluded that the point defects induced in A1GaN and GaN by neutron irradiation are the dominant mechanisms responsible for performance degradations of A1GaN/GaN HEMT devices.展开更多
Direct current (DC) and pulsed measurements are performed to determine the degradation mechanisms of A1GaN/GaN high electron mobility transistors (HEMTs) under high temperature. The degradation of the DC character...Direct current (DC) and pulsed measurements are performed to determine the degradation mechanisms of A1GaN/GaN high electron mobility transistors (HEMTs) under high temperature. The degradation of the DC characteristics is mainly attributed to the reduction in the density and the mobility of the two-dimensional electron gas (2DEG). The pulsed measurements indicate that the trap assisted tunneling is the dominant gate leakage mechanism in the temperature range of interest. The traps in the barrier layer become active as the temperature increases, which is conducive to the electron tunneling between the gate and the channel. The enhancement of the tunneling results in the weakening of the current collapse effects, as the electrons trapped by the barrier traps can escape more easily at the higher temperature.展开更多
Self-heating in a multifinger A1GaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy, The device temperature is probed on the die as a function of applied bias. The operating ...Self-heating in a multifinger A1GaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy, The device temperature is probed on the die as a function of applied bias. The operating temperature of the A1GaN/GaN HEMT is estimated from the calibration curve of a passively heated A1GaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1 ℃ is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge.展开更多
Surface leakage currents of A1GaN/GaN high electron mobility transistors are investigated by utilizing a circular double-gate structure to eliminate the influence of mesa leakage current. Different mechanisms are foun...Surface leakage currents of A1GaN/GaN high electron mobility transistors are investigated by utilizing a circular double-gate structure to eliminate the influence of mesa leakage current. Different mechanisms are found under various passivation conditions. The mechanism of the surface leakage current with AI2 03 passivation follows the two-dimensional variable range hopping model, while the mechanism of the surface leakage current with SiN passivation follows the Frenkel-Poole trap assisted emission. Two trap levels are found in the trap-assisted emission. One trap level has a barrier height of 0.22eV for the high electric field, and the other trap level has a barrier height of 0.12eV for the low electric field.展开更多
Nearly lattice-matched InAIGaN/GaN heterostructure is grown on sapphire substrates by pulsed metal organic chemical vapor deposition and excellent high electron mobility transistors are fabricated on this heterostruct...Nearly lattice-matched InAIGaN/GaN heterostructure is grown on sapphire substrates by pulsed metal organic chemical vapor deposition and excellent high electron mobility transistors are fabricated on this heterostructure. The electron mobility is 1668.08cm2/V.s together with a high two-dimensional-electron-gas density of 1.43 × 10^13 cm-2 for the InAlCaN/CaN heterostructure of 2Onto InAlCaN quaternary barrier. High electron mobility transistors with gate dimensions of 1 × 50 μm2 and 4μm source-drain distance exhibit the maximum drain current of 763.91 mA/mm, the maximum extrinsic transconductance of 163.13 mS/mm, and current gain and maximum oscillation cutoff frequencies of 11 GHz and 21 GHz, respectively.展开更多
This paper investigates the impact of electrical degradation and current collapse on different thickness SiNx passivated AlGaN/GaN high electron mobility transistors. It finds that higher thickness SiNx passivation ca...This paper investigates the impact of electrical degradation and current collapse on different thickness SiNx passivated AlGaN/GaN high electron mobility transistors. It finds that higher thickness SiNx passivation can significantly improve the high-electric-field reliability of a device. The degradation mechanism of the SiNx passivation layer under ON-state stress has also been discussed in detail. Under the ON-state stress, the strong electric-field led to degradation of SiNx passivation located in the gate-drain region. As the thickness of SiNx passivation increases, the density of the surface state will be increased to some extent. Meanwhile, it is found that the high NH3 flow in the plasma enhanced chemical vapour deposition process could reduce the surface state and suppress the current collapse.展开更多
The electrical properties of A1GaN/GaN high electron mobility transistor (HEMT) with and without high-κ organic dielectrics are investigated. The maximum drain current ID max and the maximum transconductance gm max...The electrical properties of A1GaN/GaN high electron mobility transistor (HEMT) with and without high-κ organic dielectrics are investigated. The maximum drain current ID max and the maximum transconductance gm max of the organic dielectric/A1CaN/GaN structure can be enhanced by 74.5%, and 73.7% compared with those of the bare A1GaN/GaN HEMT, respectively. Both the threshold voltage VT and gm max of the dielectric/AlGaN/GaN HEMT are strongly dielectric-constant-dependent. Our results suggest that it is promising to significantly improve the performance of the A1GaN/GaN HEMT by introducing the high-κ organic dielectric.展开更多
As one of the most important tumor-associated antigens of colorectal adenocarcinoma, the carcinoembryonic antigen (CEA) threatens human health seriously ali over the globe. Fast electrical and highly sensitive detec...As one of the most important tumor-associated antigens of colorectal adenocarcinoma, the carcinoembryonic antigen (CEA) threatens human health seriously ali over the globe. Fast electrical and highly sensitive detection of the CEA with A1GaN/GaN high electron mobility transistor is demonstrated experimentally. To achieve a low detection limit, the Au-gated sensing area of the sensor is functionalized with a CEA aptamer instead of the corresponding antibody. The proposed aptasensor has successfully detected different concentrations (ranging from 50picogram/milliliter (pg/ml) to 50 nanogram/milliliter (ng/ml)) of CEA and achieved a detection limit as low as 50pg/ml at Vas = 0.5 V. The drain-source current shows a c/ear increase of 11.5μA under this bias.展开更多
Self-heating in multi-finger AlGaN/GaN high-electron-mobility transistors(HEMTs) is investigated by measurements and modeling of device junction temperature under steady-state operation.Measurements are carried out ...Self-heating in multi-finger AlGaN/GaN high-electron-mobility transistors(HEMTs) is investigated by measurements and modeling of device junction temperature under steady-state operation.Measurements are carried out using micro-Raman scattering to obtain the detailed and accurate temperature distribution of the device.The device peak temperature corresponds to the high field region at the drain side of gate edge.The channel temperature of the device is modeled using a combined electro-thermal model considering 2DEG transport characteristics and the Joule heating power distribution.The results reveal excellent correlation to the micro-Raman measurements, validating our model for the design of better cooled structures.Furthermore,the influence of layout design on the channel temperature of multi-finger AlGaN/GaN HEMTs is studied using the proposed electro-thermal model, allowing for device optimization.展开更多
AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas(2...AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas(2DEG) performance are investigated. Lowering the V/III ratio and enhancing the reactor pressure at the initial stage of the hightemperature GaN layer growth will prolong the GaN nuclei coalescence process and effectively improve the crystalline quality and the interface morphology, diminishing the interface roughness scattering and improving 2DEG mobility. AlGaN/AlN/GaN structure with 2DEG sheet density of 1.19 × 10^13cm^-2, electron mobility of 2101 cm^2·V^-1·s^-1, and square resistance of 249 Ω is obtained.展开更多
The multi-step rapid thermal annealing process of Ti/Al/Ni/Au can make good ohmic contacts with both low contact resistance and smooth surface morphology for AlGaN/GaN HEMTs.In this work,the mechanism of the multi-ste...The multi-step rapid thermal annealing process of Ti/Al/Ni/Au can make good ohmic contacts with both low contact resistance and smooth surface morphology for AlGaN/GaN HEMTs.In this work,the mechanism of the multi-step annealing process is analyzed in detail by specific experimental methods.The experimental results show that annealing temperature and time are very important parameters when optimizing the Ti/Al layer for lower resistance and the Ni/Au layer for smooth surface morphology.It is very important for good ohmic contacts to balance the rate of various reactions by adjusting the annealing temperature and time.We obtained a minimum specific contact resistance of 3.22×10^(17)Ω·cm^2 on the un-doped AlGaN/GaN structure with an optimized multistep annealing process.展开更多
The leakage current and breakdown voltage of AlGaN/GaN/AlGaN high electron mobility transistors on silicon with different GaN channel thicknesses were investigated.The results showed that a thin GaN channel was benefi...The leakage current and breakdown voltage of AlGaN/GaN/AlGaN high electron mobility transistors on silicon with different GaN channel thicknesses were investigated.The results showed that a thin GaN channel was beneficial for obtaining a high breakdown voltage,based on the leakage current path and the acceptor traps in the AlGaN back-barrier.The breakdown voltage of the device with an 800 nm-thick GaN channel was 926 V@1 m A/mm,and the leakage current increased slowly between 300 and 800 V.Besides,the raising conduction band edge of the GaN channel by the AlGaN back-barrier lead to little degradation for sheet 2-D electron gas density,especially,in the thin GaN channel.The transfer and output characteristics were not obviously deteriorated for the samples with different GaN channel thickness.Through optimizing the GaN channel thickness and designing the Al GaN back-barrier,the lower leakage current and higher breakdown voltage would be possible.展开更多
基金Project supported by the State Key Program of National Natural Science Foundation of China (Grant No 60736033)the State Key Development Program (973 Program) for Basic Research of China (Grant No 513270407)the Advanced Research Foundation of China (Grant Nos 51311050112, 51308030102 and 51308040301)
文摘AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current IDsat, maximal transconductance gm, and the positive shift of threshold voltage VTH at high drain-source voltage VDS. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEC depletion a little during the high-electric-field stress. After the hot carrier stress with VDS = 20 V and VGS= 0 V applied to the device for 104 sec, the SiN passivation decreases the stress-induced degradation of IDsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of IDsat, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted.
基金supported by the National Natural Science Foundation of China (Grant No. 60776052)
文摘In this paper we present a novel approach to modeling AlGaN/GaN high electron mobility transistor (HEMT) with an artificial neural network (ANN). The AlGaN/GaN HEMT device structure and its fabrication process are described. The circuit-based Neuro-space mapping (neuro-SM) technique is studied in detail. The EEHEMT model is implemented according to the measurement results of the designed device, which serves as a coarse model. An ANN is proposed to model AIGaN/CaN HEMT based on the coarse model. Its optimization is performed. The simulation results from the model are compared with the measurement results. It is shown that the simulation results obtained from the ANN model of A1GaN/GaN HEMT are more accurate than those obtained from the EEHEMT model.
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 No.61204085)
文摘In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized, and breakdown voltage VBR is saturated at 1085 V for gate–drain spacing LGD ≥ 8 μm. On the basis of the HEMT with a gate FP, a drain FP is added with LGD=10 μm. For the length of the drain FP LDF ≤ 2 μm, VBR is almost kept at 1085 V, showing no degradation. When LDF exceeds 2 μm, VBR decreases obviously as LDF increases. Moreover, the larger the LDF, the larger the decrease of VBR. It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the LGD at which VBR begins to saturate in the first structure. The electric field and potential distribution are simulated and analyzed to account for the decrease of VBR.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61334002,61106106,and 61204085the China Postdoctoral Science Foundation Funded Project under Grant No 2015M582610
文摘A novel A1GaN/GaN high electron mobility transistor (HEMT) with double buried p-type layers (DBPLs) in the GaN buffer layer and its mechanism are studied. The DBPL A1GaN/GaN HEMT is characterized by two equi-long p-type GaN layers which are buried in the GaN buffer layer under the source side. Under the condition of high-voltage blocking state, two reverse p-n junctions introduced by the buried p-type layers will effectively modulate the surface and bulk electric fields. Meanwhile, the buffer leakage is well suppressed in this structure and both lead to a high breakdown voltage. The simulations show that the breakdown voltage of the DBPL structure can reach above 2000 V from 467 V of the conventional structure with the same gate-drain length of 8μm.
基金Project supported by the Major Program and Key Program of National Natural Science Foundation of China (Grant Nos. 60890191 and 60736033)
文摘A1GaN/GaN high electron mobility transistors (HEMTs) were exposed to 1 MeV neutron irradiation at a neutron ftuence of 1 × 10^15 cm-2. The dc characteristics of the devices, such as the drain saturation current and the maximum transconductance, decreased after neutron irradiation. The gate leakage currents increased obviously after neutron irradiation. However, the rf characteristics, such as the cut-off frequency and the maximum frequency, were hardly affected by neutron irradiation. The A1GaN/GaN heterojunctions have been employed for the better understanding of the degradation mechanism. It is shown in the Hall measurements and capacitance voltage tests that the mobility and concentration of two-dimensional electron gas (2DEG) decreased after neutron irradiation. Tbere was no evidence of the full-width at half-maximum of X-ray diffraction (XRD) rocking curve changing after irradiation, so the dislocation was not influenced by neutron irradiation. It is concluded that the point defects induced in A1GaN and GaN by neutron irradiation are the dominant mechanisms responsible for performance degradations of A1GaN/GaN HEMT devices.
基金supported by the National Natural Science Foundation of China(Grant No.60736033)
文摘Direct current (DC) and pulsed measurements are performed to determine the degradation mechanisms of A1GaN/GaN high electron mobility transistors (HEMTs) under high temperature. The degradation of the DC characteristics is mainly attributed to the reduction in the density and the mobility of the two-dimensional electron gas (2DEG). The pulsed measurements indicate that the trap assisted tunneling is the dominant gate leakage mechanism in the temperature range of interest. The traps in the barrier layer become active as the temperature increases, which is conducive to the electron tunneling between the gate and the channel. The enhancement of the tunneling results in the weakening of the current collapse effects, as the electrons trapped by the barrier traps can escape more easily at the higher temperature.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CBA00600)the National Natural Science Foundation of China (Grant No. 61106106)the Fundamental Research Funds for the Central Universities, China (Grant No. K50510250006)
文摘Self-heating in a multifinger A1GaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy, The device temperature is probed on the die as a function of applied bias. The operating temperature of the A1GaN/GaN HEMT is estimated from the calibration curve of a passively heated A1GaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1 ℃ is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge.
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2014AA032602the National Natural Science Foundation of China under Grant Nos 61474115 and 61501421
文摘Surface leakage currents of A1GaN/GaN high electron mobility transistors are investigated by utilizing a circular double-gate structure to eliminate the influence of mesa leakage current. Different mechanisms are found under various passivation conditions. The mechanism of the surface leakage current with AI2 03 passivation follows the two-dimensional variable range hopping model, while the mechanism of the surface leakage current with SiN passivation follows the Frenkel-Poole trap assisted emission. Two trap levels are found in the trap-assisted emission. One trap level has a barrier height of 0.22eV for the high electric field, and the other trap level has a barrier height of 0.12eV for the low electric field.
基金Supported by the National Science and Technology Major Project of China under Grant No 2013ZX02308-002the National Natural Sciences Foundation of China under Grant Nos 61574108,61334002,61474086 and 61306017
文摘Nearly lattice-matched InAIGaN/GaN heterostructure is grown on sapphire substrates by pulsed metal organic chemical vapor deposition and excellent high electron mobility transistors are fabricated on this heterostructure. The electron mobility is 1668.08cm2/V.s together with a high two-dimensional-electron-gas density of 1.43 × 10^13 cm-2 for the InAlCaN/CaN heterostructure of 2Onto InAlCaN quaternary barrier. High electron mobility transistors with gate dimensions of 1 × 50 μm2 and 4μm source-drain distance exhibit the maximum drain current of 763.91 mA/mm, the maximum extrinsic transconductance of 163.13 mS/mm, and current gain and maximum oscillation cutoff frequencies of 11 GHz and 21 GHz, respectively.
基金Project supported by the State Key Program of National Natural Science Foundation of China (Grant No. 60736033)
文摘This paper investigates the impact of electrical degradation and current collapse on different thickness SiNx passivated AlGaN/GaN high electron mobility transistors. It finds that higher thickness SiNx passivation can significantly improve the high-electric-field reliability of a device. The degradation mechanism of the SiNx passivation layer under ON-state stress has also been discussed in detail. Under the ON-state stress, the strong electric-field led to degradation of SiNx passivation located in the gate-drain region. As the thickness of SiNx passivation increases, the density of the surface state will be increased to some extent. Meanwhile, it is found that the high NH3 flow in the plasma enhanced chemical vapour deposition process could reduce the surface state and suppress the current collapse.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50932002)the Youth Foundation(Grant No. L08010301JX0805)+1 种基金Start-up Foundation of University of Electronic Science and Technology of China (Grant No. Y02002010301041)the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry of China (Grant No. A09010301GG-01)
文摘The electrical properties of A1GaN/GaN high electron mobility transistor (HEMT) with and without high-κ organic dielectrics are investigated. The maximum drain current ID max and the maximum transconductance gm max of the organic dielectric/A1CaN/GaN structure can be enhanced by 74.5%, and 73.7% compared with those of the bare A1GaN/GaN HEMT, respectively. Both the threshold voltage VT and gm max of the dielectric/AlGaN/GaN HEMT are strongly dielectric-constant-dependent. Our results suggest that it is promising to significantly improve the performance of the A1GaN/GaN HEMT by introducing the high-κ organic dielectric.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFB0400104 and 2016YFB0400301the National Natural Science Foundation of China under Grant No 61334002the National Science and Technology Major Project
文摘As one of the most important tumor-associated antigens of colorectal adenocarcinoma, the carcinoembryonic antigen (CEA) threatens human health seriously ali over the globe. Fast electrical and highly sensitive detection of the CEA with A1GaN/GaN high electron mobility transistor is demonstrated experimentally. To achieve a low detection limit, the Au-gated sensing area of the sensor is functionalized with a CEA aptamer instead of the corresponding antibody. The proposed aptasensor has successfully detected different concentrations (ranging from 50picogram/milliliter (pg/ml) to 50 nanogram/milliliter (ng/ml)) of CEA and achieved a detection limit as low as 50pg/ml at Vas = 0.5 V. The drain-source current shows a c/ear increase of 11.5μA under this bias.
基金Project supported by the National Basic Research Program of China(No.2011CBA00606)the National Natural Science Foundation of China(No.61106106)
文摘Self-heating in multi-finger AlGaN/GaN high-electron-mobility transistors(HEMTs) is investigated by measurements and modeling of device junction temperature under steady-state operation.Measurements are carried out using micro-Raman scattering to obtain the detailed and accurate temperature distribution of the device.The device peak temperature corresponds to the high field region at the drain side of gate edge.The channel temperature of the device is modeled using a combined electro-thermal model considering 2DEG transport characteristics and the Joule heating power distribution.The results reveal excellent correlation to the micro-Raman measurements, validating our model for the design of better cooled structures.Furthermore,the influence of layout design on the channel temperature of multi-finger AlGaN/GaN HEMTs is studied using the proposed electro-thermal model, allowing for device optimization.
基金Project support by the National Natural Science Foundation of China(Grant Nos.61474110,61377020,61376089,61223005,and 61176126)the National Science Fund for Distinguished Young Scholars,China(Grant No.60925017)+1 种基金the One Hundred Person Project of the Chinese Academy of Sciencesthe Basic Research Project of Jiangsu Province,China(Grant No.BK20130362)
文摘AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas(2DEG) performance are investigated. Lowering the V/III ratio and enhancing the reactor pressure at the initial stage of the hightemperature GaN layer growth will prolong the GaN nuclei coalescence process and effectively improve the crystalline quality and the interface morphology, diminishing the interface roughness scattering and improving 2DEG mobility. AlGaN/AlN/GaN structure with 2DEG sheet density of 1.19 × 10^13cm^-2, electron mobility of 2101 cm^2·V^-1·s^-1, and square resistance of 249 Ω is obtained.
基金supported by the National Basic Research Program of China(No.2010CB934104)
文摘The multi-step rapid thermal annealing process of Ti/Al/Ni/Au can make good ohmic contacts with both low contact resistance and smooth surface morphology for AlGaN/GaN HEMTs.In this work,the mechanism of the multi-step annealing process is analyzed in detail by specific experimental methods.The experimental results show that annealing temperature and time are very important parameters when optimizing the Ti/Al layer for lower resistance and the Ni/Au layer for smooth surface morphology.It is very important for good ohmic contacts to balance the rate of various reactions by adjusting the annealing temperature and time.We obtained a minimum specific contact resistance of 3.22×10^(17)Ω·cm^2 on the un-doped AlGaN/GaN structure with an optimized multistep annealing process.
基金supported by the Key Research and Development Program of Jiangsu Province(No.BE2016084)the National Natural Science Foundation of China(Nos.11404372,6157401,61704185)+3 种基金the Natural Science Foundation of Beijing,China(No.4182015)the Scientific Research Fund Project of Municipal Education Commission of Beijing(No.PXM2017_014204_500034)the National Key Scientific Instrument and Equipment Development Projects of China(No.2013YQ470767)the National Key Research and Development Program of China(No.2016YFC0801203)
文摘The leakage current and breakdown voltage of AlGaN/GaN/AlGaN high electron mobility transistors on silicon with different GaN channel thicknesses were investigated.The results showed that a thin GaN channel was beneficial for obtaining a high breakdown voltage,based on the leakage current path and the acceptor traps in the AlGaN back-barrier.The breakdown voltage of the device with an 800 nm-thick GaN channel was 926 V@1 m A/mm,and the leakage current increased slowly between 300 and 800 V.Besides,the raising conduction band edge of the GaN channel by the AlGaN back-barrier lead to little degradation for sheet 2-D electron gas density,especially,in the thin GaN channel.The transfer and output characteristics were not obviously deteriorated for the samples with different GaN channel thickness.Through optimizing the GaN channel thickness and designing the Al GaN back-barrier,the lower leakage current and higher breakdown voltage would be possible.