Abstract
AbstractThe 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 nGaAs (100) substrates was also investigated. After postdeposition annealing, the NH4OH passivated samples not only have a slight increase of the AsAs peaks with an appearance of As suboxide (AsOx) feature at Al2O3/GaAs interfaces but also exhibit a serious interfacial interdiffusion between Al2O3 and GaAs. However, the (NH4)2S passivated samples produce the GaS and AsS 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.
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