Influence of acceptor-like traps in the buffer on current collapse and leakage of E-mode AlGaN/GaN MISHFETs

Current collapse has been observed in transient simulations even with highly efficient surface passivation by HfO2. In this work, current collapse and buffer-leakage mechanisms in E-mode (normally off) AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors (MISHFETs) have been investigated by physics-based simulations. The influences on both current collapse and off-state leakage from the energy levels of the acceptor-like traps in the buffer and also the density of the traps have been systematically studied. It is shown that traps with higher energy levels will induce less current collapse and less buffer leakage. It is demonstrated that current collapse is closely related with the change of the densities of ionized acceptor-like traps before and after the stress. Results further indicate that with increasing buffer trap density, the off-state leakage significantly decreases while current collapse increases. Finally, a non-uniform distribution of the acceptor-like traps in the buffer has been proposed to balance the trade-off between current collapse and buffer leakage.