Zero-bias anomaly in GaAs/Mo tunnel junctions

A large zero-bias anomaly has been observed in the point contact tunnel junctions made between a degenerate p-type GaAs and Mo. The anomaly corresponds to a resistance peak centered at zero bias. The junction resistance at zero bias is a strong function of temperature, increasing with decreasing temperature. A quantitative study of the voltage and temperature dependence of the zero-bias anomaly has been made. No effect of the magnetic field up to 12 kG was found. When the temperature was lowered below the transition temperature of Mo, the superconducting energy gap of Mo was observed, which indicated that the mechanism of current flow is by electron tunneling.