Reliability of passivated and unpassivated High-k dielectric/GaAs metal-oxide-semiconductor capacitors

Metal-oxide-semiconductor (MOS) capacitors were fabricated using zirconium dioxide as a high-k dielectric layer on p-GaAs substrates with and without passivation layers. Ultrathin (1.8 nm) InP and ZnO were used as a passivation layer to prevent Fermi level pinning and regrowth of GaAs-native oxides at the interface between GaAs and ZrO₂. The trapping of charge carriers and device reliability were investigated in passivated and unpassivated GaAs MOS capacitors during electrical stress. The improved characteristics in terms of stress-induced interface trap variation, hysteresis voltage, stress induced leakage current, and flat-band voltage have been demonstrated in InP and ZnO passivated MOS devices. Time dependent dielectric breakdown properties were studied in presence of electrical stress. The breakdown time was found to be 1748 and 1703 s in InP and ZnO passivated devices, respectively, however, in unpassivated devices, it was 928 s. The InP passivated GaAs MOS devices show improved electrical and breakdown characteristics over other MOS devices.