ALUMINUM LAYERS AS NONALLOYED CONTACTS TO P-TYPE GAAS

We have investigated the electrical characteristics of a metallic alum inum layer, deposited on top of heavily doped p-type GaAs, as a means of fabricating nonalloyed ohmic contacts to epitaxial semiconductor st ructures. The aluminum layer was deposited immediately after growth by molecular beam epitaxy (MBE) of a beryllium-doped GaAs layer, i.e., w ithout exposing the sample to air, or by deposition of an aluminum lay er on the same sample in conventional vacuum evaporation equipment. Bo th types of structures were characterized via the transmission line mo del (TLM) to obtain the contact resistivity of such nonalloyed ohmic c ontacts. It appears that planar tunneling contacts grown entirely in a n MBE process show contact resistance values which are comparable to a lloyed contacts.