Absorption spectra of modulation-doped semiconductor quantum wells

Abstract

Absorption spectra of modulation‐doped GaAs–Ga1−xAlxAs semiconductor quantum wells are studied with the use of a multiband effective mass theory in which coupling of the heavy and light hole valence bands is taken into account. We consider the case in which the (GaAl)As barrier is doped with acceptors and the quantum well is populated with holes. Interband optical absorption for vertical transitions are obtained using Fermi’s golden rule in the envelope function approximation explicitly taking into account the variation of the optical matrix elements with k. Two dimensional excitonic effects are also included in a model similar to that of Shinada and Sugano but including the k dependence of the optical matrix elements. We find that the mixing of heavy and light hole states of both symmetric and antisymmetric envelope functions gives rise to direct optical transitions between all pairs of valence and conduction subbands in violation of the Δn=0 selection rule.