Real-time monitoring of InAs/GaAs quantum dot growth using ultraviolet light scattering

We present real-time measurements of surface structure evolution during quantum dot growth in InAs/GaAs grown by molecular-beam epitaxy. The measurements were made using an ultraviolet light-scattering technique in which the 254 nm line of a mercury lamp is used as the light source. This technique provides sensitivity to roughness on lateral lengthscales as low as 154 nm for our setup. Using this technique, we can detect the onset of quantum dot formation in this system, as indicated by reflection high-energy electron-diffraction measurements. The continuous increase in the scattering signal after the dots have formed, is explained in terms of diffusion-limited growth and ripening of the large islands that coexist with the quantum dots.