Optical and Transport Properties of CdSe/ZnSe Self-Organized Nanostructures: 1-Dimensional versus 3-Dimensional Quantum Confinement

We present comprehensive studies of optical, structural and transport properties of molecular beam epitaxy grown CdSe/ZnSe self-organizing nanostructures, aimed at elucidation of the intrinsic morphology of CdSe layers as a function of their nominal thickness (w). Particular attention has been paid to the layer thickness below the critical value (w < 3.0 monolayer (ML)). It is found that the layer morphology is transformed from pure two-dimensional objects at w<0.7 ML to extended (15–40 nm) flat islands formed in the thicker layers. The density of the islands increases with w, which is accompanied by enhancement of the luminescence quantum efficiency. An optically pumped green laser is fabricated, taking advantage of the superior emission characteristics of the single CdSe layer with w=2.8 ML, used as an active region. The threshold power density of 3.9 kW/cm2 observed at 300 K is fivefold less than that of the reference sample using a conventional ZnCdSe quantum-well active region.