Characterization of Undoped Pseudomorphic InGaAs/GaAs Quantum Wells by Electron Beam Electroreflectance (EBER) and Photoluminescence (PL)

We have investigated the interband optical transitions within undoped pseudomorphic In y Ga 1-y As/GaAs quantum wells of a range of thickness from 50A to 150A, and y values 0.1 to 0.2. From photoluminescence (PL), we identify the lowest interband transitions. Electron beam electroreflectance (EBER) modulation spectroscopy is utilized to detect the lowest and the higher energy interband transitions within the quantum wells. We compare the measured interband energies to those calculated theoretically. We have observed exciton-like transitions attributable to the heavy hole and light hole levels and most importantly, confined states of the split-off valence band, not reported to date. The multiplicity of observed quantum transitions allows rectangular barrier model parametrization of these wells, using hypothetical strain splitting of the various subbands. For five such quantum wells, we find the estimated indium contents and well widths to be nearly nominal, with consistent values between independent 300K and 100K data. With respect to the heavy hole subband, the conduction band offset Q c is estimated to be 0.586 ±0.024. With suitable values, all of the transitions, including those of the splitoff band, are predicted accurately.