Optical properties of hybrid quantum-well–dots nanostructures grown by MOCVD

The deposition of In _x Ga_1–x As with an indium content of 0.3–0.5 and an average thickness of 3–27 single layers on a GaAs wafer by metalorganic chemical vapor deposition (MOCVD) at low temperatures results in the appearance of thickness and composition modulations in the layers being formed. Such structures can be considered to be intermediate nanostructures between ideal quantum wells and quantum dots. Depending on the average thickness and composition of the layers, the wavelength of the photoluminescence peak for the hybrid InGaAs quantum well–dots nanostructures varies from 950 to 1100 nm. The optimal average In _x Ga_1–x As thicknesses and compositions at which the emission wavelength is the longest with a high quantum efficiency retained are determined.     

Density Control of InP/GaInP Quantum Dots Grown by Metal-Organic Vapor-Phase Epitaxy

We investigated structural and emission properties of self-organized InP/GaInP quantum dots (QD) grown by metal organic chemical vapor deposition using an amount of deposited In from 7 to 2 monolayers (ML). In the uncapped samples, using atomic force microscopy (AFM), we observed lateral sizes of 100–200 nm, together with a bimodal height distribution having maxima at ～5 and ～15 nm, which we denoted as QDs of type A and B, respectively; and reduction of the density of the type-B dots from 4.4 to 1.6 μm^–2. The reduction of the density of B-type dots were observed also using transmission electron microscopy of the capped samples. Using single dot low-temperature photoluminescence (PL) spectroscopy we demonstrated effects of Wigner localization for the electrons accumulated in these dots.