Effect of deposition parameters on the electrical and metallurgical properties of Au-Zn contacts to p-type InP
The electrical and metallurgical properties of Au-Zn contacts to p-type InP, prepared by vacuum evaporation of Au-Zn (10 wt%) alloy, were investigated as a function of deposition parameters and annealing conditions. The deposition rate of Au-Zn alloy was found to be the major factor that strongly influences the properties of as-deposited and annealed p-InP/Au-Zn contacts. At a substrate temperature of about 150 degrees C, when a high deposition rate of about 16-25 nm s-1 was used, excellent homogeneous ohmic contacts could be formed after annealing with specific contact resistance values of about 1*10-8 Omega m2 (for NA-ND=(0.8-1.0)*1024m-3). In contrast, a low deposition rate of about 0.1 nm s-1 resulted in a large scattering of resistance values and non-ohmic behaviour of contacts. In this case, a much smaller amount of zinc and its non-uniform distribution in the Au-Zn layer, as well as strong InP/Au-Zn interfacial reactions, were detected by AES and SEM techniques. The electrical and metallurgical properties of slow-deposited Au-Zn contacts could be improved by use of a lower substrate temperature (in the range of 30-50 degrees C) during contact deposition.