Threshold Voltage Improvement of Enhancement-Mode Al<inf>2</inf>O<inf>3</inf>/ AIGaN/GaN MIS-HEMT with High Drain Current Density

Abstract

We present an AlGaN/GaN high electron mobility transistor (HEMT) operating in enhancement-mode (E-mode) with metal-insulator-semiconductor (MIS) structure showing improved threshold voltage. The design includes an aluminium gallium nitride (Alo.3Gao.7N) barrier layer of 5-nm-thickness and a silicon nitride (SiN) passivation layer. The passivation layer is used for controlling the charge density of electron gas in 2-dimension (2DEG). While aluminium oxide (Ah03) on AIGaN does not change the 2DEG charge density in the hetero-interface, it increases the threshold voltage in enhancement mode. MIS-HEMT operating in E-mode shows a peak drain-current density (I DS ) of 975mA/mm and a threshold voltage (Vth) of 1.25 V. The drain current density can be increased with the increase of barrier layer charge concentration. On/off ratio and threshold voltage are compared with existing design available in literature. The significant improvement of device performance metrics can be done by controlling the charge concentration and the thickness of Alo.3Gao.7N barrier layer.