Fabrication Of T-Gate Algan/Gan Heterostructure Field Effect Transistor With Thermally Stable Schottky Contact

The effective Schottky barrier height of an Ir contact was increased on annealing up to 500 degreesC in O-2 ambient. The barrier height was increased by about 0.3 eV compared to that of an as-deposited Ir contact and reverse leakage current dramatically decreased after annealing. The IrO2 formed by annealing played a role in increasing the effective Schottky barrier height and prevented inter-diffusion of Ir atoms to the AlGaN layer, and led to a thermally stable Schottky contact for the gate electrode of an AlGaN/GaN heterostructure field effect transistor. The fabricated device had I-max = 628 mA/mm and G(m,max) = 245 mS/mm, with a T-shaped gate of L-g = 0.8 mum and W-g = 25 x 2 mum.