A method was developed for determining the surface diffusion coefficient and activation energy of Ge adatoms on (001). That is, Ge self-assembled quantum dots which were grown on a relaxed SiGe buffer-layer nucleated preferentially over a network of buried 60° dislocations. The surface sites over the buried dislocations acted as sinks for Ge adatoms. When the average dislocation spacing became larger than the surface diffusion length of Ge adatoms, denuded zones which were free from Ge self-assembled quantum dots appeared on both sides of buried dislocations and separated preferentially nucleated self-assembled quantum dots from randomly nucleated ones. The denuded zone width and the inter-dot spacing of randomly nucleated self-assembled quantum dots depended completely upon the surface diffusion coefficient. By varying the substrate temperature during growth, the activation energy for surface diffusion could be determined from the equilibrium inter-dot spacing of randomly nucleated Ge self-assembled quantum dots. The pre-exponential term in the diffusion constant could also be determined by using Fick’s first law, and the observation that the total incident flux of Ge adatoms which impinged on the denuded zones equalled the average rate of volume increase of self-assembled quantum dots over dislocations. The diffusion of Ge adatoms on Si (001) could be described by:

D (cm2/s) = 2.53 x 10-7 exp[-0.676(eV)/kT]

at 650 to 725C.

A Technique for the Measurement of Surface Diffusion Coefficient and Activation Energy of Ge Adatom on Si(001). H.J.Kim, Z.M.Zhao, J.Liu, V.Ozolins, J.Y.Chang, Y.H.Xie: Journal of Applied Physics, 2004, 95[11], 6065-71