Ohmic Contacts to p-GaAs with Au/Zn/Au Structure

A reproducible technique for forming ohmic contacts with low contact resistances to p-GaAs is presented. A Au/Zn/Au multilayer structure, which is deposited by sequential evaporation of Au, Zn and Au, is found to realize a satisfactorily low specific contact resistance r c . The value of r c is minimized when the initial thickness of Zn layer is larger than 200 Å and the alloying temperature is around 400°C. The minimum value of r c in Ω-cm 2 is expressed as r c =1.8×10 18 · p -1.3 , where p is the net hole concentration in cm -3 . It is also confirmed by Auger spectroscopy that the reduction of r c is caused by the preferential incorporation of Zn atoms into the GaAs bulk during alloying.