Annealing-Modulated Surface Reconstruction for Self-Assembly of High-Density Uniform InAs/GaAs Quantum Dots on Large Wafers Substrate

In this work, we developed pre-grown annealing to form & beta;2 reconstruction sites among & beta; or & alpha; (2 x 4) reconstruction phase to promote nucleation for high-density, size/wafer-uniform, photoluminescence (PL)-optimal InAs quantum dot (QD) growth on a large GaAs wafer. Using this, the QD density reached 580 (860) & mu;m(-2) at a room-temperature (T) spectral FWHM of 34 (41) meV at the wafer center (and surrounding) (high-rate low-T growth). The smallest FWHM reached 23.6 (24.9) meV at a density of 190 (260) & mu;m(-2) (low-rate high-T). The mediate rate formed uniform QDs in the traditional & beta; phase, at a density of 320 (400) & mu;m(-2) and a spectral FWHM of 28 (34) meV, while size-diverse QDs formed in & beta;2 at a spectral FWHM of 92 (68) meV and a density of 370 (440) & mu;m(-2). From atomic-force-microscope QD height distribution and T-dependent PL spectroscopy, it is found that compared to the dense QDs grown in & beta; phase (mediate rate, 320 & mu;m(-2)) with the most large dots (240 & mu;m(-2)), the dense QDs grown in & beta;2 phase (580 & mu;m(-2)) show many small dots with inter-dot coupling in favor of unsaturated filling and high injection to large dots for PL. The controllable annealing (T, duration) forms & beta;2 or & beta;2-mixed & alpha; or & beta; phase in favor of a wafer-uniform dot island and the faster T change enables optimal T for QD growth.