Parabolic quantum wells with theGaAs−AlxGa1−xAssystem

Abstract

Photoluminescence measurements at 5 K on wafers containing parabolic quantum wells fabricated by molecular-beam expitaxy with the GaAs-${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As system reflect harmonic oscillator-like electron and hole levels. The many observed heavy-hole transitions can be fitted accurately with a model that divides the energy-gap discontinuity ${\Delta E}_g$ equally between the conduction and valence-band wells. This is in marked contrast to the usual ${\Delta E}_c=0.85\mathrm{}{\Delta E}_g$ and ${\Delta E}_v=0.15\mathrm{}{\Delta E}_g$ generally assumed for square wells. Experiment and theory show that parabolic wells can lead to parity-allowed $\Delta n=2\mathrm{}$ ("forbidden") transitions with strengths greater than that of nearby $\Delta n=0\mathrm{}$ ("allowed") transitions.