POLARIZATION ANISOTROPY OF SUBBAND 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 spectru m of InxGa1-xP layers grown on GaAs (001) substrates. At a given energ y in the sub-band gap region, the peak strength of these oscillatory f eatures decreases from a positive maximum to a negative minimum passin g through zero as the polarization of the incident probe beam is rotat ed by 90 degrees from [1(1) over bar0$] direction to [110] direction i n the (001) plane. The origin of this phenomenon is explained on the b asis 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 t o reproduce the polarization dependent observations quite well. (C) 19 98 American Institute of Physics.