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Impact of the Al/Hf ratio on the electrical properties and band alignments of atomic-layer-deposited HfO2/Al2O3 on S-passivated GaAs substrates

HfO2, Al2O3 and HfO2/Al2O3 (AHO) nanolaminates with various Al/Hf ratios (including 1:3.0, 1:2.1 and 1:1.3) were fabricated on S-passivated GaAs substrates by atomic layer deposition (ALD). The interface structure and band alignments of various dielectric/GaAs structures have been investigated systematically. The AHO films with the Al/Hf ratio of 1:1.3 suppress the formation of As oxides and elemental As overlayers around AHO/GaAs interfaces more effectively than other samples, showing higher accumulation capacitance, less hysteresis width (ΔVFB = 415 mV) and lower leakage current density. The band alignments of interfaces of HfO2/GaAs, Al2O3/GaAs and AHO/GaAs were established. The results indicate that ALD HfO2/Al2O3 nanolaminate structures could effectively tune the interface quality and band offset of gate dielectric films on n-GaAs.