Comparison of (111)- and (001)-grown GaAs-AlxGa1-xAs quantum wells by magnetoreflectance

Magnetoreflectance studies on GaAs/AlxGa1-xAs quantum wells grown on (111) and (001) substrates have been performed in magnetic fields from 0 to 9 at 4.2K. Excitonic transitions of 1s, 2s, 3s,... states are observed and identified for the transitions from the first heavy-hole subband to the first electron subband and from the first light-hole subband to the first electron subband in the well. From the diamagnetic shifts, we have determined the reduced effective masses, and the binding energies for excitons in the well using several different methods. A comparison of the reduced masses of the excitons in the (111) and (001) samples determined experimentally gives a ratio of 111/001=0.92. We have also attempted to deduce the heavy-hole and light-hole effective masses perpendicular and parallel to the (111) axis, and the band parameters.