InAs quantum dots with size fluctuations of less than 4% were grown on GaAs using the self-assembling method. By covering the quantum dots with In0.2Ga0.8As or In0.2Al0.8As, strain in InAs dots can be partly reduced due to relaxation of lattice constraint in the growth direction. This results in low-energy emission (about 1.3 μm) from the quantum dots. The photoluminescence linewidth can be reduced to 21 meV at room temperature. This width is completely comparable to the theoretical limit of a band-to-band emission from a quantum well at room temperature. Because the dots can be uniformly covered by the strain reducing layers, factors that degrade size uniformity during coverage, such as compositional mixing or segregation, will be suppressed, allowing for an almost ideal buried quantum dot structure.

Effects of rapid thermal annealing on the optical properties of In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As multiple quantum wells with InGaAs and dielectric capping layers Influence of a thin AlAs cap layer on optical properties of self-assembled InAs/GaAs quantum dots Appl. Phys. Lett. 75, 3968 (1999); 10.1063/1.125509Suppression of temperature sensitivity of interband emission energy in 1.3-m-region by an InGaAs overgrowth on self-assembled InGaAs/GaAs quantum dots

The shape of InAs quantum dots grown on GaAs substrates by molecular beam epitaxy is investigated at various growth temperatures. A dot with a new shape surrounded by {110} facets and having a high aspect ratio appears at temperatures over 510 °C. This dot is transformed from a pyramid shape (low aspect ratio) when its volume exceeds a critical value by raising the growth temperature. The shape transition indicates that the high-aspect-ratio dot is energetically favorable at a large volume. A narrow energy width of photoluminescence, 35 meV at room temperature, is obtained by the growth of the high-aspect-ratio dots, which have a fairly good size uniformity of less than 4% deviation.

Strong optical anisotropy is observed in the photoluminescence ͑PL͒ bands of both the InP self-assembled quantum dots and the Ga 0.5 In 0.5 P matrix. From the linearly polarized PL spectra measured under weak excitation, we found that large size quantum dots show strong anisotropy. The luminescence from a single quantum dot observed by the micro-PL technique revealed a doublet fine structure of the exciton levels that obey the linear polarization selection rule. The observed fine structure is shown to arise from an interplay of the electron-hole exchange interaction and the asymmetric crystal structure of the InP/Ga 0.5 In 0.5 P system. ͓S0163-1829͑99͒50608-5͔ RAPID COMMUNICATIONS

InAs quantum dots (QDs) with a high density of 9×1010 cm−2 are formed on InAlGaAs layer/InP (311)B substrates. Lasers having five-period stacked InAs QD layers are operated in the ground state (λ≈1.6 μm) at room temperature, and the maximal modal gain of the ground state is measured to be 20 cm−1. We obtained a threshold current density of 380 A/cm2 at room temperature, and observed the temperature-insensitive threshold current at temperatures from 77 to 220 K.