Magnetotransport properties of two-dimensional electron gases （2DEG） in AlxGa1-x N/GaN heterostructures with different Al compositions are investigated by magnetotransport measurements at low temperatures and in hig...Magnetotransport properties of two-dimensional electron gases （2DEG） in AlxGa1-x N/GaN heterostructures with different Al compositions are investigated by magnetotransport measurements at low temperatures and in high magnetic fields. It is found that heterostructures with a lower Al composition in the barrier have lower 2DEG concentration and higher 2DEG mobility.展开更多
We report an Al0.25Ga0.75N/GaN based lateral field emission device with a nanometer scale void channel. A -45 nm void channel is obtained by etching out the SiO2 sacrificial dielectric layer between the semiconductor ...We report an Al0.25Ga0.75N/GaN based lateral field emission device with a nanometer scale void channel. A -45 nm void channel is obtained by etching out the SiO2 sacrificial dielectric layer between the semiconductor emitter and the metal collector. Under an atmospheric environment instead of vacuum conditions, the OaN- based field emission device shows a low turn-on voltage of 2.3 V, a high emission current of -40 μA （line current density 2.3mA/cm） at a collector bias Vc = 3 V, and a low reverse leakage of 3nA at Vc = -3 V. These characteristics are attributed to the nanometer scale void channel as well as the high density of two-dimensional electron gas in the AlGaN/GaN heterojunction. This type of device may have potential applications in high frequency mieroelectronics or nanoelectronics.展开更多
Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the polarization sheet charge density and relative permittivity a...Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the polarization sheet charge density and relative permittivity are analyzed and calculated by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the values of relative permittivity and polarization sheet charge density of AlN/GaN diode are both much smaller than the ones of AlGaN/GaN diode, and also much lower than the theoretical values. Moreover, by fitting the measured forward 1-V curves, the extracted dislocations existing in the barrier layer of the AlN/GaN diode are found to be much more than those of the AlGaN/GaN diode. As a result, the conclusion can be made that compared with AlGaN/GaN diode the Schottky metal has an enhanced influence on the strain of the extremely thinner AlN barrier layer, which is attributed to the more dislocations.展开更多
Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as...Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an A1GaN/GaN diode by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostrncture results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an A1GaN/GaN diode.展开更多
Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. Whil...Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. While the carrier concentration reaches 1.32×10^13 cm^-2 and stays relatively unchanged with the decreasing temperature, the mobility of the 2DEG increases to 1.21 × 10^4 cm2/（V.s） at 2 K. The Shubnikov-de Haas （SdH） oscillations are observed in a magnetic field as low as 2.5 T at 2 K. By the measurements and the analyses of the temperature-dependent SdH oscillations, the effective mass of the 2DEC is determined. The ratio of the transport lifetime to the quantum scattering time is 9 in our sample, indicating that small-angle scattering is predominant.展开更多
We report Al0.30Ga0.70N//GaN/Al0.07Ga0.93N double heterostructure high electron mobility transistors with a record saturation drain current of 1050mA/mm. By optimizing the graded buffer layer and the GaN channel thick...We report Al0.30Ga0.70N//GaN/Al0.07Ga0.93N double heterostructure high electron mobility transistors with a record saturation drain current of 1050mA/mm. By optimizing the graded buffer layer and the GaN channel thickness, both the crystal quality and the device performance are improved signiflcantly, including electron mobility promoted from 1535 to 1602 cm2//V.s, sheet carrier density improved from 0.87× 10^13 to 1.15× 10^13 cm^-2, edge dislocation density reduced from 2.5× 10^10 to 1.3× 10^9 cm^ -2, saturation drain current promoted from 757 to record 1050mA/mm, mesa lealmge reduced by two orders in magnitude, and breakdown voltage promoted from 72 to 108 V.展开更多
文摘Magnetotransport properties of two-dimensional electron gases （2DEG） in AlxGa1-x N/GaN heterostructures with different Al compositions are investigated by magnetotransport measurements at low temperatures and in high magnetic fields. It is found that heterostructures with a lower Al composition in the barrier have lower 2DEG concentration and higher 2DEG mobility.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No BK20160400the Science and Technology Project of Suzhou under Grant No SZS201508
文摘We report an Al0.25Ga0.75N/GaN based lateral field emission device with a nanometer scale void channel. A -45 nm void channel is obtained by etching out the SiO2 sacrificial dielectric layer between the semiconductor emitter and the metal collector. Under an atmospheric environment instead of vacuum conditions, the OaN- based field emission device shows a low turn-on voltage of 2.3 V, a high emission current of -40 μA （line current density 2.3mA/cm） at a collector bias Vc = 3 V, and a low reverse leakage of 3nA at Vc = -3 V. These characteristics are attributed to the nanometer scale void channel as well as the high density of two-dimensional electron gas in the AlGaN/GaN heterojunction. This type of device may have potential applications in high frequency mieroelectronics or nanoelectronics.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.61306113,60876009,and 11174182)
文摘Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the polarization sheet charge density and relative permittivity are analyzed and calculated by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the values of relative permittivity and polarization sheet charge density of AlN/GaN diode are both much smaller than the ones of AlGaN/GaN diode, and also much lower than the theoretical values. Moreover, by fitting the measured forward 1-V curves, the extracted dislocations existing in the barrier layer of the AlN/GaN diode are found to be much more than those of the AlGaN/GaN diode. As a result, the conclusion can be made that compared with AlGaN/GaN diode the Schottky metal has an enhanced influence on the strain of the extremely thinner AlN barrier layer, which is attributed to the more dislocations.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.60890192,60876009,and 11174182)
文摘Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an A1GaN/GaN diode by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostrncture results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an A1GaN/GaN diode.
基金Project supported by the National Basic Research Program of China (Grant No.2011CB309606)
文摘Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. While the carrier concentration reaches 1.32×10^13 cm^-2 and stays relatively unchanged with the decreasing temperature, the mobility of the 2DEG increases to 1.21 × 10^4 cm2/（V.s） at 2 K. The Shubnikov-de Haas （SdH） oscillations are observed in a magnetic field as low as 2.5 T at 2 K. By the measurements and the analyses of the temperature-dependent SdH oscillations, the effective mass of the 2DEC is determined. The ratio of the transport lifetime to the quantum scattering time is 9 in our sample, indicating that small-angle scattering is predominant.
基金Supported by the National Science and Technology Major Project of China under Grant No 2013ZX02308-002the National Natural Science Foundation of China under Grant Nos 11435010 and 61474086
文摘We report Al0.30Ga0.70N//GaN/Al0.07Ga0.93N double heterostructure high electron mobility transistors with a record saturation drain current of 1050mA/mm. By optimizing the graded buffer layer and the GaN channel thickness, both the crystal quality and the device performance are improved signiflcantly, including electron mobility promoted from 1535 to 1602 cm2//V.s, sheet carrier density improved from 0.87× 10^13 to 1.15× 10^13 cm^-2, edge dislocation density reduced from 2.5× 10^10 to 1.3× 10^9 cm^ -2, saturation drain current promoted from 757 to record 1050mA/mm, mesa lealmge reduced by two orders in magnitude, and breakdown voltage promoted from 72 to 108 V.
