Characterization of Traps and Trap-Related Effects in Recessed-Gate Normally-off AlGaN/GaN-based MOSHEMT

Traps and trap-related effects in recessed-gate normally-off AlGaN/GaN-based MOSHEMT with SiO2 gate dielectric were characterized. Hysteresis in ID-VG was observed at elevated temperature (similar to 120 degrees C) due to the traps. To understand the traps, current transient in drain was investigated at given gate and drain pulses with different temperatures. Two groups of time constants were extracted: one is nearly constant and the other is decreased with temperature. Extracted activation energies from the drain current transients with temperature are 0.66 eV and 0.73 eV, respectively, for given gate and drain pulses. Using extracted exponential trap density profile from frequency dependent conductance method [4], we could understand C-V behavior with frequency. It was shown that traps inside AlGaN layer are a main cause for the decrease of capacitance at high frequency in inversion region. The pulsed I-V characteristics also show frequency dependence.