Comparative study of Ti∕Al∕Mo∕Au, Mo∕Al∕Mo∕Au, and V∕Al∕Mo∕Au ohmic contacts to AlGaN∕GaN heterostructures

Abstract

Ohmic contact formation by Ti∕Al∕Mo∕Au, Mo∕Al∕Mo∕Au, and V∕Al∕Mo∕Au on AlGaN∕GaN heterostructure field effect transistor layers have been studied and compared. Mo∕Al∕Mo∕Au ohmic contacts exhibited the lowest contact resistance of 0.22±0.02Ωmm over a range of anneal temperatures from 650to800°C. The minimum contact resistances of Ti∕Al∕Mo∕Au and V∕Al∕Mo∕Au ohmic contacts were measured to be 0.38±0.04Ωmm at an anneal temperature of 800°C and 0.35±0.07Ωmm at an anneal temperature of 700°C, respectively. Long-term thermal stability measurements were performed at 500, 600, and 700°C. Of the three metallization schemes, Ti∕Al∕Mo∕Au exhibited the best thermal stability (up to 8.5h at 700°C). Intermetallic reactions were investigated using Auger electron spectroscopy and x-ray diffraction measurements.