Three beam photoreflectance as a powerful method to investigate semiconductor heterostructures

We have proposed three beam photoreflectance (TBPR) technique as a powerful tool to investigate the nature of PR resonances associated with transitions in quantum wells (QWs) placed in a weak surface electric field. This method works as a contactless forward bias and allows changing the internal fields even down to the flat band conditions. We have shown that changes in built-in electric field by amount of a few tenths of kV/cm can modify the transition intensities significantly whereas the transition energies are being kept unchanged and no Stark shift of the QW energy levels is detected. The intensity changes make it possible to distinguish between the parity allowed and forbidden optical transitions in a quantum well