Use of Sn-doped GaAs for non-alloyed ohmic contactsto HEMTs

Abstract
Segregation of Sn to the surface of MBE grown n+-GaAs layers allows fabrication of non-alloyed Ti/Pt/Au, Al or Ti/W ohmic contacts with low specific contact resistivities (1.1 × 10-6 Ω·cm2). These contacts were used to realise high performance HEMTs (gm = 230 mS/mm for 1.0 µm gate length) in which Si is used as the dopant in the donor AlGaAs layer and Sn is employed in the GaAs contact layer.