Pd/Pt/Au and AuGe/Ni/Pt/Au ohmic contacts for AlSb/InAs HEMTs

We report on the fabrication and characteristics of Pd/Pt/Au and AuGe/Ni/Pt/Au ohmic contact metalizations for AlSb/InAs HEMTs. For the AuGe/Ni/Pt/Au contact, a contact resistance of 0.11 /spl Omega/-mm was achieved using a 300/spl deg/C rapid thermal anneal. Auger depth profiling revealed considerable Au in-diffusion. Using this contact, 0.2 /spl mu/m gate-length AlSb/InAs HEMTs were fabricated which exhibit a low-field source-drain resistance of 0.61 /spl Omega/-mm and a transconductance of 1.3 S/mm. For the Pd/Pt/Au contact, a contact resistance of 0.08 /spl Omega/-mm was achieved using a 175/spl deg/C hot plate heat treatment. Auger depth profiling revealed that the diffusion of the Pd/Pt/Au contact is significantly less than that of the AuGe/Ni/Pt/Au contact. Using the Pd/Pt/Au contact, 0.5 /spl mu/m gate-length AlSb/InAs HEMTs were fabricated which exhibit a low-field source-drain resistance of 0.47 /spl Omega/-mm.