New observation of internal transitions of neutral and negatively charged donors by optically detected resonance spectroscopy

Abstract

We report an optically detected resonance (ODR) study of neutral and negatively charged donors in GaAs/AlGaAs quantum well structures. The intensity of the e(1)h(1) excitonic reflectance feature was modulated by resonant absorption of a monochromatic far-infrared (FIR) laser beam. The magnetic field was applied externally to bring the internal transitions among several impurity states into resonance with the far-infrared (FIR) photon energy. Internal transitions of neutral and negatively charged donors at the edge of the well were observed and were found to be in good agreement with theoretical calculations. These results demonstrate that the reflectance-based ODR technique is a useful tool for the study of donor states in semiconductor quantum wells.