X-Ray Diffraction Analysis on Gallium-Indium Interdiffusion in Quantum Dot Superlattices

Thermal induced interdiffusion in InAs/GaAs quantum dot superlattices is studied by high-resolution x-ray diffraction rocking curve and photoluminescence techniques. With increasing annealing temperature, up to 300 meV a blueshift of the emission peak position and down to 16.6 meV a narrowing of the line width are found in photoluminescence spectra, and respective intensity of the higher-order satellite peaks to lower-order ones in the x-ray rocking curves decreases. Dynamical theory is employed to simulate the measured x-ray diffraction data. Excellent agreement between the experimental curves and the simulations is achieved when the composition, thickness and stress variations caused by interdiffusion are taken into account. It is found that the significant In-Ga intermixing occurs even in the as-grown InAs/GaAs quantum dots. The estimated diffusion coefficient is 1.8 x 10^-17cm².s^-1 at 650°C, 3.2 x 10^-17cm².s^-1 at 750°C, and 1.2 x 10^-14cm².s^-1 at 850°C.