Γ-X electron level crossover in ZnSe/BeTe multiple quantum wells -: art. no. 113307

We report on the photoluminescence (PL) properties of thin BeTe/ZnSe/BeTe type II quantum wells (QW's), where the Gamma electron level in ZnSe is close to the resonance with the X electron level in BeTe. The Gamma-X levels crossover modifies the nature of the interband optical transitions which are indirect in real space but direct in k space for the thick enough QW's and direct in real space but indirect in k space for the QW's thinner than 2-3 monolayers. Approaching the crossover condition from the side of thicker QW's leads to a thresholdlike quenching and spectral narrowing of the PL band. The latter effect can be explained taking into account the inhomogeneous broadening of the Gamma electron level.