Comparison of (111)- and (001)-grown GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells by magnetoreflectance

Magnetoreflectance studies on GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As 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, ${\mathrm{\mu }}_{\mathrm{\perp }}$, 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 ${\mathrm{\mu }}_{111\mathrm{\perp }}$/${\mathrm{\mu }}_{001\mathrm{\perp }}$=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.