Optically biased photoreflectance spectroscopy of a GaAs epitaxial layer and an AlGaAs/GaAs quantum well

We propose optically biased photoreflectance (OBPR) spectroscopy, which is performed by continuous illumination of a secondary monochromatic light on a sample with conventional photoreflectance (PR), as a useful tool to investigate the internal electric fields dependence of the PR signals associated with band to band and quantum level transitions. Line shape of the PR signal has a strong dependence on the internal electric field. In OBPR, if a secondary incident light is absorbed, the internal electric field is suppressed by the photo-generated electron–hole pairs. On the other hand, if the secondary light is not absorbed, the internal electric field is not affected. Through the OBPR investigation of a GaAs epitaxial layer and an AlGaAs/GaAs quantum well, we are able to obtain an absorption like spectrum by performing a wavelength scan of a secondary monochromatic light. The results of OBPR measurements at each PR peak position show the contribution of the electric fields modification by the photo-generated carriers in each layers to the PR signals that are related to band gap and quantum level transitions.