Structural characterization of the interfacial reactions between palladium and gallium arsenide

Abstract

X-ray diffraction was performed in situ at temperatures from 25–550 °C to investigate the process of compound formation at the interface between evaporated Pd thin films (∠1000 Å thick) and GaAs single crystals. For heating in 1 atm argon, the interfacial reactions occurred at temperatures above ∠250 °C—isothermal heating at 250 °C resulted in the appearance of PdGa and a small amount of Pd2Ga after 30–40 min; isothermal heating at 350 °C resulted in the appearance of Pd2Ga, PdGa, and PdAs2 after 15–20 min; isothermal heating at 500 °C resulted in the appearance of PdGa alone after ∠5 min. The PdAs2 phase was found to be a surface layer which could be removed mechanically by ultrasonic cleaning or by the use of an adhesive tape. Removal of PdAs2 was indicated by ex situ x-ray diffraction results, which showed the disappearance of the PdAs2 diffraction peaks and the enhancement of the PdGa peaks. For heating in vacuum (10−6 Torr), the interfacial reactions occurred at temperatures above ∠200 °C—the appearance of PdGa and a small amount of Pd2Ga was observed after ∠15 min of heating at 200 °C; PdAs2 was not observed at any temperature.