Electrical characteristics of Al_2O_3/TiO_2/Al_2O_3 prepared by atomic layer deposition on (NH_4)_2S-treated GaAs

摘要

The electrical characteristics of atomic layer deposited (ALD) Al_2O_3/TiO_2/Al_2O_3 on (NH_4)_2S treated GaAs MOS capacitor were studied. The electrical characteristics were improved from the reduction of native oxides and sulfur passivation on GaAs by (NH_4)_2S treatment. The top high bandgap ALD-Al_2O_3 can further reduce the thermionic emission, and the bottom ALD-Al_2O_3 improves the interface state density by the self-cleaning. The high dielectric constant TiO_2 is used to lower the equivalent oxide thickness. The leakage currents can reach 8.3×10~(-9) and 2.2×10~(-7)A/cm~2 at ±2 MV/cm, respectively. The interface state density is 3.11 × 10~(11)cm~(-2)eV~(-1) at the energy of about 0.57 eV from the edge of the valence band.