Reverse-bias stress of high electron mobility transistors: Correlation between leakage current, current collapse and trap characteristics

Abstract

This paper describes an investigation of the effect of reverse-bias stress on the leakage current and trapping characteristics of GaN based HEMT. The analysis is based on combined electrical, transient and electroluminescence measurements, carried out during the execution of step-stress experiments. The experimental data collected within this work indicate that: (i) when submitted to reverse bias stress, beyond a certain critical voltage, the devices can show a significant increase in leakage current, which is correlated to the generation of luminescence spots, that can be identified by means of EL measurements; (ii) beyond the critical voltage, the increase in gate leakage is correlated to an increase in current collapse; (iii) transient measurements, carried out to get information on the origin of current collapse, identify the existence of two trap levels (T1 and T2). Results suggest that stress does not induce the generation of new defective levels, but only the increase in the amplitude of the current transients associated to pre-existing traps.