Optical and magnetic resonance studies of As-impurities in AlSb: from isoelectronic point defects to planes

Strong photoluminescence (PL) has been observed and assigned to excitons from superlattices (SL) composed of fractional or single planes of As atoms separated by 8-49 monolayers (ML) of AlSb, from a single As-impurity sheet embedded in AlSb, and from AlSb layers uniformly doped with As. The emission ( similar to 1.40-1.62 eV) from the SLs exhibits a weak dependence on period but a strong dependence on the amount of As in the plane. From optically detected magnetic resonance, the g-values and strength of the exchange interaction indicate that the SL recombination involves an exciton whose electron is strongly localized at the As-planes and whose hole is excluded to the AlSb layers. This assignment is supported by ab initio total energy calculations of the electronic band structure. Similar PL was found from the sample with a single As-impurity sheet. A PL band at 1.606 eV from the As-doped AlSb layer is ascribed to recombination of excitons bound to As-impurities that substitute isoelectronically on the Sb sites. (C) 1999 Elsevier Science B.V. All rights reserved.