Effects of rapid thermal annealing on the electrical properties and the strain of the AlGaN/AlN/GaN heterostructure field-effect transistors with Ni/Au gate electrodes

In this study, we investigated the electrical properties and the strain of the AlGaN/AlN/GaN heterostructure field-effect transistors with Ni/Au gate electrodes using the measured capacitance-voltage (C-V) and current-voltage (I-V) characteristics and the polarization effect of the heterostructures. We found that the Ni/Au gate electrode showed a good thermal stability when the RTA temperature is below 400 A degrees C; however, with further increase in the annealing temperature, the 2DEG sheet density under the Ni/Au Schottky contact started to decline dramatically, and the device started to exhibit bad pinch-off characteristics after a 700 A degrees C RTA. We also found that the RTA process could change the strain and even damaged the crystal structure of the barrier layer under the gate electrodes.