Alloying behavior of Ni/Au-Ge films on GaAs

Abstract

Alloying behavior of thin Ni/Au‐Ge films deposited on a GaAs substrate is investigated by using a microprobe Auger spectrometer and an x‐ray diffractometer. The deposited films react with the substrate above 300 °C to form alloys with complex multilayer structure in the 300–400 °C temperature range and alloys with microscopic grain structure above 450 °C. Uniform alloying, accompanied with a smooth interface, is observed and is ascribed to the high reactivity of Ni with GaAs under a solid‐solid phase. However, when the sample is annealed in the solid‐solid phase, Ni penetrates irregularly into the GaAs substrate, if the annealing duration is too long, causing poor Ohmicity. Rapid Ge moving to the substrate interface is observed at 400 °C and is closely related to the formation of a Ge‐doped degenerate layer beneath the contact. The high reliability of the contract, which is obtained when annealed at 500 °C, is explained by the metallurgical stability of the grain structure. Based on the results of this study, some rules for III‐V compound semiconductor contact fabrication are proposed.