Photoreflectance spectroscopy of low-dimensional GaAs/AlGaAs structures

Results of room-temperature photoreflectance measurements on three GaAs/Al-0.33 Ga0.67As multiquantum well (Mow) structures with three different widths of wells and on two GaAs/Al0.33Ga0.67As high-electron-mobility transistor (HEMT) structures are presented. Energy-gap-related transitions in GaAs and AlGaAs were observed. The Al content in AlGaAs was determined. MQW transition energies were determined using the first derivative of a Gaussian profile of the measured resonances. In order to identify the transitions in the MQS, the experimentally observed energies were compared with results of the envelope function calculation method for a rectangular quantum well. The Franz-Keldysh oscillation (FKO) model was also used to determine the built-in electric field in various parts of the investigated structures. The values of the electric fields allow us to hypothesise about the origin of these fields. (C) 1997 John Wiley & Sons, Ltd.