Real-time stress evolution during Si1-xGex Heteroepitaxy: Dislocations, islanding, and segregation

Abstract

We have used sensitive real-time measurements of film stress during Si~_xGe x molecular beam epitaxy to examine strain relaxation due to coherent island formation, and to probe the kinetics of Ge surface segregation. We first describe our novel curvature-measurement technique for real-time stress determination. Measurements of the relaxation kinetics during high temperature Si79Ge21 growth on Si (001) are reported in which formation of highly regular arrays of {501]-faceted islands produce 20% stress relaxation. An island shape transition is also observed that reduces the effective stress by up to 50% without dislocations. Nonuniform composition profiles due to Ge surface segregation during growth of planar alloy films are determined with submonolayer thickness resolution from the real-time stress evolution. Up to two monolayers of Ge can segregate to the growth surface.

The dynamic competition between stress generation and relaxation mechanisms during coalescence of Volmer–Weber thin films

“…The data are plotted as stress-thickness vs thickness, where the slope of the curves represents an "incremental" stress associated both with growth of new film, and relaxation occurring within the existing film [12]. Note that positive values of stress-thickness imply a tensile mean stress (i.e., spatially averaged through the film), while negative values imply a compressive mean stress.…”

Monitoring and Controlling of Strain During MOCVD of AlGaN for UV Optoelectronics

“…This technique provides a direct measurement of the stress during deposition and is described in detail in Ref. [17].…”

In situ detection of an initial elastic relaxation stage during growth of In0.2Ga0.8As on GaAs(0 0 1)

“…The initial linear behaviour corresponds to the pseudomorphic growth regime. In this regime, each deposited monolayer incorporates the same amount of stress, which corresponds to the misfit strain   Consequently, the accumulated stress increases linearly with thickness and its slope allows to determine the composition x of the In x Ga 1-x As layers [9,13]. For the samples shown in Fig.…”

“…For this purpose, the 350 m thick GaAs substrates were shaped as cantilevers along [110] direction and mounted on a special substrate holder which allowed free bending of the sample. Substrate curvature and accumulated stress in the layers () are related by the Stoney's equation [9,10]. The layer relaxation and the In composition were obtained from the in situ accumulated stress measurements and also from ex situ X-ray diffraction.…”

“…In the last years, a new in situ stress characterization technique, based on substrate curvature optical monitorization, has been successfully used in order to study stress relaxation during the growth of SiGe/Si [9] and III-V compounds [10,11]. This technique has been successful in providing direct experimental evidence of elastic relaxation as a consequence of the formation of 3D nanostructures.…”