Leakage current from non-alloyed metal on carbon controlled semi-insulating GaAs crystals

Leakage of carbon-controlled semi-insulating GaAs crystals was investigated using various pairs of n-type (AuGe, with alloying), non-alloyed (Au) and p-type (AuZn, with alloying) electrodes. Large leakage currents were observed under two conditions: when positive voltage was applied to non-alloyed or p-type electrode with opposite-side electrode of n-type. This leakage had no relation to carbon concentration which determine the semi-insulating properties. Properties of the non-alloyed electrode were found to be very similar to those of p-type electrode. A model is proposed which can explain all the results, taking into account band-bending near the electrode.