Temperature dependence of photoluminescence of CdSe/ZnSe quantum dots grown on GaAs and Si/Ge virtual substrates

Abstract

We have carried out temperature-dependent studies of the photoluminescence properties of a set of CdSe/ZnSe quantum dot structures grown on conventionally used GaAs(100) substrates and Si(100)/Ge virtual substrates. Both single-layer and multilayer QD structures have been studied. It was shown that the conventional MBE technique allows to grow CdSe/ZnSe QDs having the activation energy of luminescence quenching as large as 200 meV. Such issues as possible reasons of such a large activation energy and exciton migration in QD planes are discussed.1 Introduction Growth of self-assembled II-VI and III-V quantum dots (QDs) on Si substrates is of a crucial importance for the integration of optoelectronic devices with the mainstream silicon-based technology. It is difficult to obtain high-quality ZnSe epilayers directly on the Si substrate due to large lattice mismatch between these semiconductors. ZnSe and Ge have close lattice constants and, consequently, Ge is more convenient material for growing ZnSe-based heterostructures than Si. In principle, a sequence of epitaxial layers can be grown on Si substrates which has Ge-layer with relatively high structural quality as a cap layer. Such epitaxial structure can be used as a substrate (so-called "virtual" substrate) for growth of ZnSe.A new technique of growth of high-quality CdSe/ZnSe QD structures on virtual Si(100)/Ge substrates has recently been developed by our group. TEM and X-ray studies have showed that high-quality selfassembled CdSe/ZnSe QD structures could be grown on Si/Ge virtual substrates [1]. It was established also that the photoluminescence (PL) efficiency of such structures is comparable with those of analogous QD structures grown on GaAs substrates [2].It is important for design of II-VI QD blue-green laser structures and light-emitting devices integrated with the silicon-based technology and operated at room temperature to study the influence of structure parameters on the temperature dependence of their luminescent properties. Studies of the PL temperature dependence of CdSe/ZnSe QDs grown on conventionally used GaAs (100) substrates and Si(100)/Ge virtual substrates are reported.