Use of Au/Te/Ni films for ohmic contact to GaAs

Ohmic contacts to n-type GaAs are usually fabricated by alloying AuGe/Ni films on GaAs. Ge acts as a donor to GaAs for fabrication of the ohmic contact. In an attempt to replace Ge, which is an amphoteric impurity, with a group VI element to improve on the ohmic contact resistivity, experiments were done with AuTe and AuTe/Ni contacts. A very low resistivity of about 5 x 10 to the -7th ohm/sq cm was obtained by alloying 1700 A of AuTe film with 300 A of nickel on top at 510 C. This is the lowest contact resistivity obtained with any material other than AuGe/Ni on n-type GaAs.