Optical study of spatially ordered InAs quantum dots in disk-like structures

Abstract

InAs quantum dots (QD) made by self‐assembled growth naturally have a random spatial and large spectral distribution. However the spatial and spectral profile of an optical cavity mode are highly predictable. To achieve the maximum interaction of single QD spontaneous emission (SE) with a cavity mode, QDs should ideally be spatially located in the cavity mode, but well isolated from nearby nonradiative surface recombination. To solve this issue, we have developed a patterned regrowth technique to place QDs near the antinode of a cavity mode. We show that the regrowth process does not affect the QDs optical properties while maintaining reasonable cavity quality factors. The PL signature of our QDs is discussed. We identify the single excitons, charged excitons and bi‐excitions. Their relative intensities are decided by the excessive energy of free carriers and tunable by the sample temperature. In our research, we see strong evidence of disk sizing effect, which provide additional method to control the QD density besides material deposition and growth temperature. With this additional tunability, the QD density can be adjusted to produce low numbers of QDs (1∼3 dots) per disk, so the optimal coupling of a single QD with a single cavity mode is quite plausible.