Al-free Ti/Mo/Ta/Au-based n-type ohmic contact with a smooth surface for AlGaN/GaN power HEMTs

摘要

We have demonstrated an Al-free Ti/Mo/Ta/Au-based n-type ohmic contact for high power AlGaN/GaN high electron mobility transistors (HEMTs). Our fabricated ohmic contact has an extremely smooth surface morphology and almost the same specific contact resistance (ρ_c) of 9.1 x 10~(-6) Ωcm~2 as conventional Ti/Al-based contacts. We have found that Mo, which is generally inserted as a barrier layer, has the effect of reducing contact resistance. Moreover, we have applied this ohmic technique to fabricate an AlGaN/GaN HEMT and obtained sufficient transconductance (g_m) of 210 mS/mm.