Influence of Trap State Effects on Buffer Leakage Current and Breakdown Voltage in Nano-Channel AlGaN/GaN DHFETs

Influence of deep level trap states on the buffer leakage current of enhancement-mode AlGaN/GaN/AlGaN double-heterostructure FETs (DHFETs) has been studied. The effect of trap density and trap energy level on the buffer leakage current and the breakdown voltage is discussed. Simulation shows that the increase of trap density and energy level leads to a dramatic reduction of leakage current flowing through the AlGaN buffer layer. The breakdown voltage increases linearly with the trap density. The breakdown voltage is improved by deepening the energy level of traps until it reaches 0.5 eV under the conduction band of the AlGaN buffer. The optimized trap density and energy level for DHFETs is 1 x 10(16) cm(-3) and 0.5 eV, respectively. On the other hand, the breakdown voltage increases linearly with the gate-to-drain distance, being consistent with experimental result and the highest breakdown voltage of 2300 V is achieved by optimization.