Polarization anisotropy of sub-band gap oscillatory features in contactless electroreflectance spectrum of InxGa1-xP layers grown on GaAs (001) substrates

We report the observation of strongly polarization sensitive sub-band gap oscillatory features in the contactless electroreflectance spectrum of InxGa1-xP layers grown on GaAs (001) substrates. At a given energy in the sub-band gap region, the peak strength of these oscillatory features decreases from a positive maximum to a negative minimum passing through zero as the polarization of the incident probe beam is rotated by 90 degrees from [1(1) over bar0$] direction to [110] direction in the (001) plane. The origin of this phenomenon is explained on the basis of optical interference coupled with linear electro-optic effect induced changes in the sub-band gap refractive index of the InxGa1-xP layers. Numerical simulations based on the above mechanism are shown to reproduce the polarization dependent observations quite well. (C) 1998 American Institute of Physics.