A Hybrid Schottky–Ohmic Drain Contact for Thermally Stressed Beta‐Gallium Oxide Field‐Effect Transistors

Abstract

Degradation of ohmic contacts on β-Ga 2 O 3 under thermal stress conditions is a severe issue that hinders its high-temperature applicability. Herein, a hybrid Schottky-ohmic drain contact (HSD) is demonstrated in β-Ga 2 O 3 field-effect transistors (FETs). It is compared with a conventional ohmic drain contact (OD) after extended thermal annealing. Pulsed drain bias measurement is conducted to investigate the trapping process at the interface of both drain contacts with the β-Ga 2 O 3 channel. Even with the extended Schottky metal region, the β-Ga 2 O 3 FET with the HSD contact exhibits similar contact and on-resistance. Additionally, it shows field-effect mobility higher than that of the OD contact device. Enhanced off-state breakdown characteristics are achieved.

A 2.8 kV Breakdown Voltage α-Ga2O3 MOSFET with Hybrid Schottky Drain Contact

“…The oxide capacitance (C OX ) is calculated to be 712 nF/cm 2 . The μ FE of the HSD device is lower than the OD device at V DS = 1 V because the α-Ga 2 O 3 /Ni Schottky junction was not turned on completely, and this can affect the current’s flow toward the drain [ 29 ]. In the saturation region, a high V DS of 40 V induces current paths beneath the Schottky region, and thus similar levels of μ FE were obtained.…”

“…compares extracted field-effect m (µFE) of the OD and HSD devices for variable LSD at VDS = 1 V and 40 V. The µFE is cal by µFE = gm • LSD/(W • COX • VDS) in the linear region and µFE = 2 • slope 2 /(COX • (W/L saturation region.The oxide capacitance (COX) is calculated to be 712 nF/cm 2 . Th the HSD device is lower than the OD device at VDS = 1 V because the α-Ga2O3/Ni S junction was not turned on completely, and this can affect the current's flow tow drain[29]. In the saturation region, a high VDS of 40 V induces current paths bene Schottky region, and thus similar levels of µFE were obtained.…”

“…Alternatively, the hybrid Schottky–Ohmic drain (HSD) scheme utilizing charge trapping in the Schottky extension region can be considered because of the relatively inferior crystal quality of heteroepitaxial α-Ga 2 O 3 compared to the homoepitaxial Ga 2 O 3 layer [ 25 , 26 , 27 , 28 ]. Indeed, the use of HSD on β-Ga 2 O 3 FETs has been reported to alleviate degradation under thermal stress conditions [ 29 ].…”