Aluminium layers as nonalloyed contacts to p-type GaAs

Abstract

We have investigated the electrical characteristics of a metallic aluminum layer, deposited on top of heavily doped p‐type GaAs, as a means of fabricating nonalloyed ohmic contacts to epitaxial semiconductor structures. The aluminum layer was deposited immediately after growth by molecular beam epitaxy (MBE) of a beryllium‐doped GaAs layer, i.e., without exposing the sample to air, or by deposition of an aluminum layer on the same sample in conventional vacuum evaporation equipment. Both types of structures were characterized via the transmission line model (TLM) to obtain the contact resistivity of such nonalloyed ohmic contacts. It appears that planar tunneling contacts grown entirely in an MBE process show contact resistance values which are comparable to alloyed contacts.