Effects of grown-in defects on interdiffusion dynamics in InAs∕InP(001) quantum dots subjected to rapid thermal annealing

Abstract

This work investigates the interdiffusion dynamics in self-assembled InAs∕InP(001) quantum dots (QDs) subjected to rapid thermal annealing in the 600–775°C temperature range. We compare two QD samples capped with InP grown at either optimal or reduced temperature to induce grown-in defects. Atomic interdiffusion is assessed by using photoluminescence measurements in conjunction with tight-binding calculations. By assuming Fickian diffusion, the interdiffusion lengths LI are determined as a function of annealing conditions from the comparison of the measured optical transition energies with those calculated for InP∕InAs1−xPx∕InP quantum wells with graded interfaces. LI values are then analyzed using a one-dimensional interdiffusion model that accounts for both the transport of nonequilibrium concentrations of P interstitials from the InP capping layer to the InAs active region and the P–As substitution in the QD vicinity. It is demonstrated that each process is characterized by a diffusion coefficient D(i) given by D(i)=D0(i)exp(−Ea(i)∕kBTa). The activation energy and pre-exponential factor for P interstitial diffusion in the InP matrix are Ea(P–InP)=2.7±0.3eV and D0(P–InP)=103.6±0.9cm2s−1, which are independent of the InP growth conditions. For the P–As substitution process, Ea(P–As)=2.3±0.2eV and (co∕no)D0(P–As)∼10−5−10−4cm2s−1, which depend on the QD height and concentration of grown-in defects (co∕no).