Investigation of metal contacts on semi-insulating GaAs: Physics, technology and applications

The work reports on a study of the symmetric metal/SI GaAs/metal (M-S-M) diodes in order to demonstrate the effect of contact metal work function. We compare the high work function Pt contact versus the low work function Mg contact. The Pt-S-Pt, Mg-S-Mg and Mg-S-Pt structures are characterized by the current-voltage measurements. The Mg-S-Pt structure show a significant current decrease at low bias while the Mg-S-Mg structure shows saturation current at high voltages more than an order of magnitude lower with respect to the Pt-S-Pt reference. The phenomena observed in Mg-containing samples are explained by the presence of insulating MgO layer at the M-S interface. The reported findings have potential applications in sensors based on SI GaAs.