Characterization of GaAs/InGaAs quantum wells using photocurrent spectroscopy

We report on characterization studies of high quality metal-organic vapor phase epitaxy and molecular beam epitaxy grown GaAs/InGaAs quantum wells, set within p-i-n diodes, to determine the well widths, indium mole fractions, and conduction band offset. We present photocurrent spectra containing a larger number of transitions than revealed in photoluminescence or photoluminescence excitation experiments. The energies of these transitions have been modeled using a theoretical characterization tool known as ‘‘contouring,’’ which is used in this strained system for the first time. This has enabled determination of the conduction band offset in GaAs/InGaAs quantum wells, to a value between 0.62 and 0.64, for a range of indium fractions between 0.155 and 0.23. As a final, additional check on our results, we compare the field dependence of the e1-hh1 exciton transition energy with our theoretical calculations and find good agreement.