Differential reflectance spectroscopy using sample rotation

Differential reflectance (DR) is one of the modulation spectroscopies, and its modulation signal arises from the differential reflectance due to the s patial inhomogeneity of the sample. There are several methods to achieve th e difference reflectance and we report here an experimental configuration u sing sample rotation. This configuration looks similar to that adopted prev iously by reflectance difference spectroscopy (RDS), however in the DR expe riments we trace the signal synchronizing with the fundamental rotation fre quency (f) of the sample. In RDS one used the second harmonic frequency of the rotation (2f) as the reference frequency. We check this method with an InGaAs/GaAs quantum well and an AlGaAs/GaAs heterojunction bipolar transist or (HBT). Both samples show well resolved spectral features which are in go od agreement with photoreflectance measurements. (C) 1999 American Institut e of Physics. [S0034-6748(99)02003-1].