Photoluminescence of InGaAs/InP quantum dots

The spatial distribution of photo-excited carriers in dry etched InGaAs/InP quantum-well-dots (QWDs) has been investigated by photoluminescence (PL) spectroscopy and cathodoluminescence (CL) imaging. High resolution e-beam lithography and CH₄/H₂ reactive ion etching were used to fabricate QWDs from multiple quantum well (MQW) heterostructures with GaAs well thicknesses ranging from 1 to 15 nm. Low temperature CL spectra from a single QWD stack provided a measure of the layer-to-layer variation in intensity in such MQW dots. Lateral distributions of emission intensity in single quantum dots and dot-to-dot variations in emission intensity have been obtained from CL line scans. The QWD PL intensity from the thicker, bottom QWDs in a stack is found to increase relative to the PL from the thinner, top QWDs with increasing excitation intensity and increasing temperature. This observation is attributed to the diffusion of carriers generated in the InP substrate into the bottom quantum wells. The PL spectra of all five 128 nm diameter QWDs in the MQW stacks exhibit a blueshift of about 3 meV at the lowest excitation intensity