The dependence of barrier height inhomogeneity on the gate metal has been investigated for the AlGaN/GaN Schottky diode. The analysis from the electroreflectance spectroscopy measurement for different types of Schottky gate metals tried (in this case, Au, Pt, Pd, and Ni) reveals that the surface donor states of AlGaN/GaN heterostructure strongly depends on the type of Schottky gate metals used, which suggests that barrier height inhomogeneity is strongly dependent on the gate metal. The X-ray photoelectron spectroscopy also reveals a strong correlation between the barrier height inhomogeneity and the gate metal type.

Dominant nonradiative recombination mechanisms as a function of nonradiative current were investigated in InGaN blue light-emitting diodes (LEDs). Each radiative and nonradiative current components were separated from the total current by using the information of the internal quantum efficiency (IQE), obtained from the temperature-dependent electroluminescence measurement. By analyzing voltage and light output power as functions of nonradiative current, we were able to understand that the dominant nonradiative mechanisms of the LEDs vary with the competing mechanisms of Shockley-Read-Hall or tunneling recombination at low current density to the carrier overflow at high current density, inducing the IQE droop. #

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In this work, the impact of trap states at the p-(Al)GaN/AlGaN interface has been investigated for the normally-off mode p-(Al)GaN/AlGaN/GaN heterostructure field-effect transistors (HFETs) by means of frequency dependent conductance. From the current–voltage (I–V) measurement, it was found that the p-AlGaN gate integrated device has higher drain current and lower gate leakage current compared to the p-GaN gate integrated device. We obtained the interface trap density and the characteristic time constant for the p-type gate integrated HFETs under the forward gate voltage of up to 6 V. As a result, the interface trap density (characteristic time constant) of the p-GaN gate device was lower (longer) than that of the p-AlGaN. Furthermore, it was analyzed that the trap state energy level of the p-GaN gate device was located at the shallow level relative to the p-AlGaN gate device, which accounts for different gate leakage current of each devices.

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