Performance Enhancement of Norma11y-Off Plasma-Assisted Atomic Layer Deposited AI2O3/GaN Metal-Oxide-Semiconductor Field-Effect Transistor with Postdeposition Annealing

摘要

A normally-off GaN-based metal-oxide-semiconductor field effect transistor (MOSFET) was fabricated using the Alo.3Gao.7N/GaN heterostructure with a two-dimensional electron gas (2DEG) density of ~1×10~(14) cm~(-2) grown on a silicon substrate. The AIGaN layer in the gate region was fully recessed and the whole surface of the device was covered with a high-quality plasma-assisted atomic-layer-deposited (PAALD) Al_2O_3 layer, which plays the role of not only a gate insulator in the recessed gate region, but also a surface passivation layer in the ungated region between the source and the drain. The fabricated Al_2O_3/GaN MOSFET exhibited excellent device properties, such as a threshold voltage of 1.1 V extrapolated in the linear region at a drain voltage of 0.1 V, maximum drain current of 353mA/mm, field-effect mobility of 225cm~2·V~(～1)·s~(～1), and on-resistance of 9.7Ω·mm, which are among the best values ever reported for GaN MOSFETs fabricated on silicon substrates.