Influence of ZnSe capping of CdSe layers in the growth mode of ZnCdMgSe/CdSe/ZnCdMgSe heterostructures

Abstract

The authors present a photoluminescence study of the optical and structural properties of ZnSe/CdSe/ZnSe layers grown by atomic layer epitaxy, embedded within barriers of ZnCdMgSe lattice-matched to the InP (001) substrate. The authors show that a few ZnSe monolayers surrounding the CdSe layer inhibit quantum dot formation and induce the growth of quantum islands of CdSe. For the case of a 2 monolayers coverage of CdSe, quantum islands of 1 and 2 monolayers thickness were observed. These quantum islands (or quantum terraces) present intense luminescence even at room temperature.

Strain Compensation in Single ZnSe/CdSe Quantum Wells: Analytical Model and Experimental Evidence

“…On the contrary, when grown on an In x Ga 1– x As substrate with higher Indium content, resulting in a lattice constant in-between those of ZnSe and CdSe, one layer is tensile strained (ZnSe) while the other is compressively strained (CdSe). Strain compensation is widely used in stacked quantum dots and multiple quantum wells to reduce the overall strain build-up and corresponding relaxation toward the upper layers of the stack. − To analyze the strain components in both directions in nanoscopic layer stacks with a spatial resolution in the range of (sub)­nanometers, only few techniques are suitable. , X-ray diffraction and Raman spectroscopy allow very precise strain resolution but the spatial resolution is limited to some hundreds nanometers. Transmission electron microscopy (TEM) based strain measurements have a significantly higher spatial resolution, while the strain resolution is slightly worse.…”