Ohmic contact to p-type GaAs using Cu3Ge

We have investigated epsilon(1)-Cu3Ge as an ohmic contact to p-type GaAs, and found that the epsilon(1)-Cu3Ge contact has a specific contact resistivity of 5x10(-6) Omega cm(2) on p-type GaAs with doping concentrations of similar to 7x10(18) cm(-3). The epsilon(1)-Cu3Ge contact exhibits a planar and structurally abrupt interface with the GaAs, and no reaction between the contact metal and the GaAs is required for contact formation. The contact is electrically stable during annealing at temperatures up to 400 degrees C. It is suggested that Ge is incorporated into the GaAs as a p-type impurity resulting in a low contact resistivity. Furthermore, the addition of Ge to Cu to form epsilon(1)-Cu3Ge is found to impede the diffusion of Cu into the p-type GaAs. Along with the results reported for n-type GaAs, the present results indicate that epsilon(1)-Cu3Ge is an attractive candidate for ohmic contact formation on both n- and p-type GaAs. (C) 1999 American Institute of Physics. [S0003-6951(99)00251-X].