ACTIVATED STRAIN RELIEF OF Ge/Si(100) ISLANDS

Abstract

Stress concentration at the boundary of Ge/Si(100) islands drives strain relief mechanisms activated at higher growth temperature, T. Si interdiffusion for T≥ 550° C forms a reduced misfit alloy allowing specific cluster morphologies to exist at sizes greater than those for pure Ge islands. This interdiffusion also affects the pathway for island shape changes. Trenches formed at the island base result from diffusion of the most highly strained material to regions of lower strain and precede dislocation formation for T≥ 600° C .

Composition of Ge(Si) islands in the growth of Ge on Si(111) by x-ray spectromicroscopy

“…play the shape of a truncated pyramid, with a triangular base, which evolves into a more asymmetric-faceted configuration upon further growth. 12,31,33,34 Our results are qualitatively consistent with Raman-scattering measurements performed on micrometersized Ge/ Si islands on Si͑001͒ mesas, which displayed comparable features. In some cases, such mass depletion results in the exposure of the WL.…”

Microstructural evolution of Ge/Si(100) nanoscale islands

“…The formation of trenches at the bases of large Ge islands becomes more prevalent at higher growth temperatures [12][13][14][15]28,29], and this type of morphology has been attributed to diffusion of highly strained material towards regions of lower strain. Detailed profile analysis using tapping- mode AFM has been used to establish a linear dependence of the trench depth on the island base width [13].…”

“…Fig. 13 summarizes the overall facet evolution as a function of diameter for Ge islands grown at 700 C. Transition structures [10,14,32,33] having shapes intermediate between pyramids and domes are observed for diameters, d; in the range 90odo145 nm, mostly coherent dome clusters exist in the approximate range 145odo210 nm, and only dislocated dome clusters are found at larger diameters. Using EELS analysis, we also discovered that the coherent dome clusters had an average composition of Si 0.59 Ge 0.41 , independent of their size [16].…”

“…It is also recognized that slow Ge deposition rates allow Ge/Si islands to adopt the height, width and distribution of dislocations required to minimize their energy [4]. However, Ge/Si intermixing [9,11,12] and trench formation around island perimeters [9,[12][13][14][15] have also been shown to represent alternative strain-relief mechanisms that are activated at higher growth temperatures. Transmission electron microscopy (TEM) methods have been indispensable in the process of documenting these various microstructural features.…”

Ge/Si(100) Island and Wetting Layer Composition

“…Si interdiffusion into nominally pure Ge islands grown on the Si(100) surface has been intensively investigated [1][2][3][4][5][6][7]. Si incorporation into the islands reduces their strain energy, leading to different morphology evolution and alters their optical and electronic properties.…”