AlN/Al0.5Ga0.5N HEMTs with heavily Si-doped degenerate GaN contacts prepared via pulsed sputtering

Abstract

This paper reports AlN barrier Al0.5Ga0.5N high electron mobility transistors (HEMTs) with heavily Si-doped degenerate GaN contacts prepared by pulsed sputtering deposition. Selectively regrown n-type GaN contacts exhibit typical degenerate properties with the electron concentration and mobility of 2.6 × 1020 cm−3 and 115 cm2 V−1 s−1, respectively, resulting in a record low contact resistance R C of 0.43 Ω mm for the AlN/Al0.5Ga0.5N HEMTs. The AlN/Al0.5Ga0.5N HEMTs displayed a remarkable DC output characteristic with a maximum drain current density of 250 mA mm−1, a transconductance of 32 mS mm−1, and an On/Off ratio >106. The present results show potential overcoming challenges in ohmic contact formation for high-power and high-frequency AlGaN electron devices with high Al composition.