Atomic and electronic structures of oxides on III-V semiconductors

The surface reconstructions of decapped InAs(001) and In 0.53Ga0.47As(001) have been studied using scanning tunneling microscopy (STM). Quantitative comparison of the In0.53Ga 0.47As(001)-(4x2) and InAs(001)-(4x2) show the reconstructions are almost identical, but In0.53Ga0.47As(001)-(4x2) has at least a 4x higher surface defect density even on the best samples. For both In0.53Ga0.47As(001)-(4x2) and InAs(001)-(4x2), density functional theory (DFT) simulations at elevated temperature are consistent with the experimentally observed 300 K structure being a thermal superposition of three structures.;The passivation of InAs(001) and InGaAs(001) surface using three different oxides (SiO, Ga2O and In2O) was studied using STM, STS, and DFT modeling of bonding and electronic structures. SiO molecules have higher self-binding energy so that they bond themselves and form nanoclusters on InAs(001)-(4x2) surface. Conversely, both Ga2O and In 2O molecules bond to the As atoms at the edge of the rows. However, Ga2O molecules also bond to preexisting Ga2O oxide on the surface. At full coverage with post-deposition annealing, SiO oxide remains as nanoclusters, Ga2O oxide forms disordered structures with the large flat terraces on the surface, while In2O oxide bonds with the trough In atoms to form new O-In bonding sites and forms ordered structures running in the [110] direction on In0.53Ga0.47As(001)-(4x2). STS results show that Ga2O oxide does not passivate the interface nor unpin the In0.53Ga0.47As(001)-(4x2) surface consistent with its inability to form monolayer ordered islands on the surface; conversely, In2O/In0.53Ga0.47As(001)-(4x2) has an ordered monolayer coverage and is unpinned.