Thermal reaction of gold metallization on InP

Abstract

The thermal reaction of evaporated Au films with InP substrate has been studied using scanning electron microscopy, secondary ion mass and Auger electron spectroscopy, and x-ray diffraction techniques in the temperature range 345–460 °C. Below 450 °C, In and P out-diffusion with In being the faster diffusing species, as well as Au in-diffusion have been found to take place to form Au2P3 and Au3In phases at the Au-InP interface and in the outer region of the Au layer, respectively. The kinetics of P penetration into Au and Au penetration into InP have been determined to be controlled by diffusion kinetics with an activation energy of 2.31 eV. At the temperature above 450 °C, only AuIn2 phase has been found to form within the original InP bulk leaving a planar surface and facets on the {111} P planes. Microstructures, in-depth composition profiles and binary phases observed in the present experiment have been correlated in terms of Au-InP solid state interaction at various temperatures. Based on the result of this study, methods of obtaining Au-based contacts to InP with high stability have been discussed. The use of thin metallization has been found to be effective to restrict the Au-semiconductor reaction. This has been applied to the p contact of InGaAsP/InP light emitting diode and its improved stability has been confirmed under current stress experiments.