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

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 L_I are determined as a function of annealing conditions from the comparison of the measured optical transition energies with those calculated for InP/InAs_1-xP_x/InP quantum wells with graded interfaces. L_I 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(-E_a⁽ⁱ⁾/k_BT_a). The activation energy and pre-exponential factor for P interstitial diffusion in the InP matrix are E_a^(P–InP)=2.7±0.3 eV and D₀^(P–InP)=10^3.6±0.9 cm² s^-1, which are independent of the InP growth conditions. For the P–As substitution process, E_a^(P–As)=2.3±0.2 eV and (c_o/n_o)D₀^(P–As)∼10^-5-10^-4 cm² s^-1, which depend on the QD height and concentration of grown-in defects (c_o/n_o). [ABSTRACT FROM AUTHOR]