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AlGaN/GaN heterostructures have been irradiated by neutrons with different fluences and characterized by means of temperature-dependent Hall measurements and Micro-Raman scattering techniques. It is found that the carrier mobility of two-dimensional electron gas (2DEG) is very sensitive to neutrons. At a low fluence of 6.13 × 1015 cm[?]2, the carrier mobility drops sharply, while the sheet carrier density remains the same as that of an unirradiated sample. Moreover, even for a fluence of up to 3.66 × 1016 cm[?]2, the sheet carrier density shows only a slight drop. We attribute the degradation of the figure-of-merit (product of ns × m) of 2DEG to the defects induced by neutron irradiation. Raman measurements show that neutron irradiation does not yield obvious change to the strain state of AlGaN/GaN heterostructures, which proves that degradation of sheet carrier density has no relation to strain relaxation in the present study. The increase of the product of ns × m of 2DEG during rapid thermal annealing processes at relatively high temperature has been attributed to the activation of GeGa transmuted from Ga and the recovery of displaced defects. [ABSTRACT FROM AUTHOR]

Pt/AlGaN/AlN/GaN Schottky diodes are fabricated and characterized for hydrogen sensing. The Pt Schottky contact and the Ti/Al/Ni/Au ohmic contact are formed by evaporation. Both the forward and reverse currents of the device increase greatly when exposed to hydrogen gas. A shift of 0.3V at 300K is obtained at a fixed forward current after switching from N2 to 10%H2+N2. The sensor responses under different concentrations from 50ppm H2 to 10%H2+N2 at 373K are investigated. Time dependences of the device forward current at 0.5V forward bias in N2 and air atmosphere at 300 and 373K are compared. Oxygen in air accelerates the desorption of the hydrogen and the recovery of the sensor. Finally, the decrease of the Schottky barrier height and sensitivity of the sensor are calculated. [ABSTRACT FROM AUTHOR]

The valence band offset (VBO) of an Al0.17Ga0.83N/GaN heterojunction is determined to be 0.13 ± 0.07 eV by x-ray photoelectron spectroscopy. From the obtained VBO value, the conduction band offset (CBO) of ~0.22 eV is obtained. The results indicate that the Al0.17Ga0.83N/GaN heterojunction exhibits a type-I band alignment. [ABSTRACT FROM AUTHOR]

An InxGa1[?]xN/InN quantum-dot intermediate-band solar cell is calculated by means of solving the Schrodinger equation according to the Kronig--Penney model. Based on particular assumptions, the power conversion efficiency is worked out. The results reveal that the InxGa1[?]xN/InN quantum-dot intermediate-band solar cell manifests much larger power conversion efficiency than that of p-n junction solar cells, and the power conversion efficiency strongly depends on the size of the quantum dot and the interdot distance. [ABSTRACT FROM AUTHOR]

Electrical properties of Aly Ga1-yN/AlxGa1-xN/AlN/GaN structure are investigated by solving coupled Schrodinger and Poisson equation self-consistently. Our calculations show that the two-dimensional electron gas (2DEG) density will decrease with the thickness of the second barrier (AlyGa1-yN) once the AlN content of the second barrier is smaller than a critical value yc, and will increase with the thickness of the second barrier (AlyGa1-yN) when the critical AlN content of the second barrier yc is exceeded. Our calculations also show that the critical AlN content of the second barrier yc will increase with the AlN content and the thickness of the first barrier layer (AlxGa1-xN). [ABSTRACT FROM AUTHOR]