Ar RIE to improve the source/drain contact in GaN HEMT

In this work, we introduce an effective yet low cost method to improve the Ohmic contact in the AlGaN/GaN HEMT. Even with high temperature annealing, the source/drain contact shows Schottky behavior with a large turn-on voltage (V
_ON
) which limits the ON current of the transistor, especially under low operation voltage. An extra Ar reactive ion etching (RIE) performed after the O
₂
RIE is found to largely improve the source/drain contact. The Schottky contact with high V
_ON
is converted to Ohmic contact with negligible V
_ON
under a moderate Ar RIE power. The relation between the Ar RIE power and V
_ON
is studied systematically revealing an interesting trend. This effect is due to the recess of the AlGaN layer by the Ar RIE, similar to that etched by the Cl-based inductive coupled plasma (ICP). Compared to Cl-based ICP, Ar RIE has lower production cost, better environmental compatibility and is less hazardous to human health.