Exciton binding energies from an envelope function analysis of data on narrow quantum wells of integral monolayer widths in AlGaAs/GaAs.

Heavy and light hole exciton transitions were observed from isolated quantum wells in two wafers of Al sub (0.4) Ga sub (0.6) As/GaAs produced by molecular beam epitaxy using interrupted growth at the heterointerfaces. The transitions can be assigned to well widths that are integral multiples of a GaAs monolayer width with the integers between 6 and 25. Direct measurements of the barrier layer band gap and barrier layer exciton binding energy were also made. A detailed envelope function analysis of this unique data set revealed the necessity of using a soft- edge potential well rather than a square well when analyzing such narrow wells. A reduction in exciton binding energies of 2.5 meV from free charge arising from unintentional barrier doping of ~ 1 x 10 sup (14) cm sup (-3) was found. Exciton binding energies for wells between 17angstroms and 70angstroms are deduced from the analysis.