Effects of periodic patterns in recessed ohmic contacts on InAlGaN/GaN heterostructures

Abstract

Pattern-recessed ohmic contacts are investigated for InAlGaN/GaN high-electron-mobility transistors (HEMTs). Periodically-recessed patterns are introduced in the source and drain contact area to achieve the lower contact resistance by making sidewall contact as well as top contact on the active mesa. The lowest ohmic contact resistance (Rc) of 0.19 Ω·mm is achieved. It is significantly lower than the contact resistance of 0.29 Ω·mm, which is obtained from the conventional ohmic contact without recessed pattern. When the proposed ohmic contact scheme is introduced in 3-μm-long gate HEMTs, the on-resistance and the maximum transconductance are improved from 2.41 Ω·mm and 320 mS/mm to 2.24 Ω·mm and 332 mS/mm, respectively. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) of the device is increased from 2.78 and 10.05 GHz to 2.97 and 10.65 GHz, respectively.