Microstructure evolution and failure mechanism for Cu/Au Schottky contacts to InGaP layer

We present the microstructure evolution and failure mechanism of Cu/Au Schottky contacts to the InGaP layer using x-ray diffractometry (XRD) and transmission electron microscopy (TEM). At annealing temperatures varying from 500 to 600°C for 1 min, the diffraction peak of the CuP ₂ alloy can be found from XRD measurement. This indicates that the Cu is unstable, because it diffused into the InGaP layer and formed a CuP ₂ alloy at annealing temperatures higher than 500°C. Furthermore, when the rapid thermal annealing temperature reached 500°C, seen from a typical cross-sectional structure in the TEM measurements, we also found a sublayer in the originally grown InGaP layer. This sublayer was identified as a mixed structure of InGaP and CuP ₂, the thickness of which increased with a rise in annealing temperature. Moreover, the failure mechanism of Cu/Au Schottky contacts to the InGaP layer could be determined from the evolution of the thickness of the sublayer at an annealing temperature of 500°C for various times. At the annealing temperature of 500°C, the activation energy between the Cu and InGaP semiconductor was 0.93 eV and the diffusion constant was 1.37×10 ³nm ²/s.