Simulation of microscopic strain in semiconducting heterojunctions

Ab initio plane wave, pseudopotential calculations within the local density approximation on GaAs/InAs and Si/AlAs (001) heterostructures are used to examine the structural features of thin layers. In GaAs/InAs computational results for the bondlength in these layers show that continuum elasticity holds down to the scale of a single inserted layer, supporting x-ray absorption fine structure spectroscopy (XAFS) against high-resolution electron microscopy (HREM) experiments. However, this is a special case and in Si/AlAs the strain is shown to be inconsistent with continuum elasticity. For Si/AlAs we also show the formation of interface electronic states on the silicon side of the interface. The difference between the two materials is attributed to charge transfer across the layer and the formation of different types of interatomic bonds in the Si/AlAs case.