Study on the reliability of AlGaN/GaN HEMTs at high temperature

Fundamentals of current conduction of the AlGaN/GaN HEMTs have been studied under the temperature ranging from 26°C to 250°C. It´s found that the maximum drain-source current (I_DS) decreases with rising temperature, and the temperature dependent of IDS has a negative coefficient of -0.31 mA/mm · °C. This deterioration mainly cause by decreasing in mobility. And a rise in temperature is accompanied with an increase in barrier height and a reduction in ideality factor. Mechanisms are suggested, including thermionic emission, field emission, trap-assisted tunneling and so on. It´s also found that reverse leakage current increases first and then decreases with rising temperature, and the dominant mechanisms are the effects of piezoelectric polarization field and variation of two-dimensional electron gas charge density. The remarkable finding is that breakdown voltage has a trend opposite to that of the reverse leakage current, and the minimum occurred at around 175 °C.