Doped Barrier Al0.65Ga0.35N/Al0.40Ga0.60N MOSHFET With SiO₂ Gate-Insulator and Zr-Based Ohmic Contacts

This letter reports an Al0.65Ga0.35N-Al0.4Ga0.6N metal–oxide–semiconductor–heterojunction–field–effect–transistor (MOSHFET) with an SiO2gate-insulator. For this first demonstration of an AlGaN channel MOSHFET, a new doped barrier epilayer design led to linear source–drain ohmic-contacts formed by Zr-based metal stack with a contact resistance as low as1.64~Ω · mm. For a device with 6-μ msource–drain opening a record saturation current of 0.6 A/mm (at gate bias of 6V) was measured. In contrast to a conventional Schottky-gate HFET, the gate-oxide from the pulsed plasma enhanced chemical vapor deposition decreased the MOSHFET gate leakage current by a factor of 104with only a 1.5-V shift in the threshold voltage. A drift mobility of 430 cm²/V· sis measured at zero-gate bias, which increases to 800 cm²/V· sclose to the threshold voltage. The device characteristics up to 250°C are used to calculate the temperature dependence of the drift mobility.