Investigation of the thermal degradation mechanism for Cu/Au Schottky contacts to the InGaP layer

Abstract

The thermal degradation mechanism of Cu/Au contacts to the InGaP layer has been investigated using current–voltage measurement, x-ray diffractometry (XRD) measurement and cross-sectional transmission electron microscopy with energy dispersive x-ray spectroscopy (EDS). The diffraction peaks of Cu, Au, and InGaP could be observed from the XRD measurement and an evident interface of Cu/InGaP also could be found from the cross-sectional microstructure. The apparent interface of Cu/InGaP was responsible for the high performance of Cu/Au Schottky contacts to the InGaP layer. The thermal stability endurance for the high performance of the Schottky contact can be maintained up to 450 °C. However, the Schottky contact performance became inferior at temperatures higher than 450 °C. At a temperature of 500 °C, the peaks of Cu and Au disappeared, the XRD measurement revealing the diffraction peaks of CuP2 and Cu3Au2 alloys. According to the cross-sectional microstructure and the EDS measurements at 500 °C, the Cu layer had been released, penetrated into the InGaP layer, and outdiffused to the Au layer to form an intermetallic layer. As a result, the thermal degradation mechanism is attributed to the release of the Cu layer and the indiffusion of Cu element to the InGaP layer.