Electrical characteristics of TiO2/Al2O3/InP capacitor after removal of native oxides by atomic layer deposited Al2O3 self-cleaning and (NH4)2S treatments

The electrical characteristics of MOS capacitor with 5/2.9 nm TiO2/Al2O3 prepared by atomic layer deposition on (NH4)2S treated InP were studied. The electrical characteristics were improved from the reduction of native oxides and sulfur passivation on InP by (NH4)2S treatment. The high dielectric constant TiO2 is used to lower the equivalent oxide thickness and the atomic force microscopy image reveals extremely flat and uniform surface. The root-mean-square roughness value of TiO2/S-InP is 0.226 nm. The stack of high bandgap Al2O3 layer can reduce the thermionic emission of low bandgap TiO2 and its self-cleaning capability further improves the interface state density. For 5/2.9 nm TiO2/Al2O3/S-InP stacked MOS capacitor, the leakage currents can reach 6.4 × 10− 8 and 7.8 × 10− 7 A/cm2 at ± 2 MV/cm, respectively. The net effective dielectric constant is 16.7. The lowest interface state density is 3.8 × 1011 cm− 2eV− 1 with a low frequency dispersion of 16%.