Thermal reaction of gold metallization on InP

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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.