Improved Device Performance in AlGaN/GaN HEMT by Forming Ohmic Contact With Laser Annealing

Abstract

An AlGaN/GaN high-electron-mobility transistor with a novel ohmic contact formation process based on conventional pulsed laser annealing is proposed. Compared with the conventional rapid thermal annealing process, the laser annealing (LA) process not only improves the surface morphology of ohmic contact metal but also exhibits a higher OFF-state breakdown voltage. An excellent rms roughness of 16.5 nm is observed by atomic force microscope which is 16.3% of the reference one. In a device with a gate-to-drain distance of 5 $\mu \text{m}$ , a forward blocking voltage of 442 V is obtained at ${V}_{\textsf {GS}} = -\textsf {8}$ V which has a 37.3% improvement compared with the conventional device. The device with LA process has lower contact resistance at actual working temperature (above 125 °C). The current transport mechanism is dominated by thermionic field emission through the ohmic contact. Moreover, the degradation of dynamic ON-resistance is significantly suppressed due to lower surface states by protecting the bare AlGaN layer from directly exposing under high temperature ambient.