Effect of surface treatments on interfacial characteristics and band alignments of atomic‐layer‐deposited Al2O3 films on GaAs substrates

The GaAs surfaces were passivated by two kinds of chemical pretreatments (using NH₄OH and (NH₄)₂S as passivation agents) for atomic layer deposited (ALD) Al₂O₃ dielectric film growth. The chemical information at Al₂O₃/GaAs interfaces was carefully characterized. The impact of surface treatments on the band alignments of ALD Al₂O₃ films on n? GaAs (100) substrates was also investigated. After postdeposition annealing, the NH₄OH passivated samples not only have a slight increase of the As? As peaks with an appearance of As suboxide (AsO_x) feature at Al₂O₃/GaAs interfaces but also exhibit a serious interfacial interdiffusion between Al₂O₃ and GaAs. However, the (NH₄)₂S passivated samples produce the Ga? S and As? S overlayers on GaAs, effectively preventing from the intermixed diffusion between Al₂O₃ films and GaAs substrates with a sharper interface. Both NH₄OH and (NH₄)₂S passivated Al₂O₃ samples show the same band gap of 6.67 eV. The conduction band offset at Al₂O₃/GaAs interface for the (NH₄)₂S passivated samples have a slight enhancement of 0.14 eV in comparison to NH₄OH passivated ones. Copyright © 2010 John Wiley & Sons, Ltd.