INVESTIGATION OF THE AG-IN-GE SYSTEM USED FOR ALLOYED CONTACTS TO GAAS

One of the useful metallization schemes for alloyed contacts to n-type GaAs consists of Ag-In-Ge. The interaction of Ag, In, and Ge within the alloy and with the GaAs substrate has been studied by Auger and photoelectron spectroscopy. In-depth profiling of the metallization scheme indicates segregation of In to the alloy GaAs interface and segregation of Ge to the surface of the alloy. Upon annealing Ge diffuses to and accumulates at the alloy GaAs interface to produce a heavily doped n** plus layer which results in ohmic electrical behavior. This is accompanied by the out diffusion of Ga to the alloy surface. Since Ge acts as a donor in GaAs when excess As exists, it compensates for the loss of Ga.