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 degrees 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/InAs1-xPx/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)=D-0((i)) exp(-E-a((i))/k(B)T(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 D-0((P-InP))=10(3.6 +/- 0.9) cm(2) 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))D-0((P-As))similar to 10(-5)-10(-4) cm(2) s(-1), which depend on the QD height and concentration of grown-in defects (c(o)/n(o)). (c) 2008 American Institute of Physics.