One-, Two-, and Three-Dimensionally Ordered GeSi Islands Grown on Prepatterned Si (001) Substrates

Abstract

Self-assembled GeSi (or Ge) islands on Si substrates have been extensively investigated not only because they represent simple model systems to understand the fundamental physics of heterostructure growth, but also because they represent promising candidates for devices compatible with sophisticated Si device integration technology [1]. On the Si substrate, GeSi or Ge initially grows in a layer-by-layer mode, and after a critical thickness is reached, islands are spontaneously formed to release misfit strain energy at the expense of an increase of surface energy. This so-called Stranski–Krastanow growth mode can occur during mismatched heterostructure growth. The growth of self-assembled GeSi or Ge islands depends on the growth process parameters [2–8], such as growth time (or deposited Ge amount), growth temperature, growth rate, and post-growth annealing. Theoretical studies of growth kinetics [9, 10] or energetics of island formation [11] came to the conclusion that a narrow island size distribution can be expected under critical growth conditions or for extremely long ripening times. In principle, taking into account the elastic interaction between neighboring islands, ordered islands can be realized [12, 13]. However, the self-assembled islands are in general randomly distributed in the growth plane due to the stochastic nucleation of the islands on a flat surface. In addition, the difference of the number density of the islands in different regions on the substrate also deteriorates the size homogeneity of the islands.