On spinodal decomposition in elastically anisotropic epitaxial films of III-V semiconductor alloys

Abstract

The elastic energy associated with alloy composition modulation in the epitaxial film of a III-V semiconductor alloy on the [001]-substrate is calculated in the analytic form. Composition modulation both in the directions parallel to the substrate surface and in the growth direction are taken into account. It is shown that the minimum of the elastic energy corresponds to the modulation along the [100]- (and/or [010]-) direction, the period of the modulation d being small compared to the film thickness h (d≪h). The ‘‘soft mode’’ of composition modulation is exponentially localized near the free surface, the localization length l being l=d/2π. The elastic energy caused by this modulation is less by the factor 1/2c11/(c11+c12) than the elastic energy corresponding to spinodal decomposition in the bulk sample. This factor is ≊1/3 for III-V alloys. Critical temperatures of spinodal decomposition Tc are calculated for a number of epitaxial ternary III-V alloys. The diffusion which occurs only in the very thin subsurface layer (nearly monolayer) is shown to provide exponential amplification of the composition modulation amplitude δc(0)∼exp(Δh/l) at early stages of the subsequent layer-by-layer growth.

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

“…We assume that the presence of this Mg-rich region initiates the formation of the second epitaxial rs-/wzMg x Zn 1-x O double layer with smaller layer thickness. As this process is related with uphill diffusion of the Mg 2+ -and Zn 2+ -ions this process is similar to spinodal decomposition observed in other compound semiconductors [35][36][37], although it describes the demixing into two phases with a different crystal structure. However, this process, which should also be observable for thick initial wz- (Fig.…”

Highly Luminescent ZnxCd1−xSe/C Core/Shell Nanocrystals: Large Scale Synthesis, Structural and Cathodoluminescence Studies

“…23,24 Nonetheless, spinodal decomposition in IIϪVI crystals has been predicted from thermodynamic considerations and observed. 25 Using high-resolution TEM, a spinodal-like phase separation was observed for Cd x Zn 1Ϫx Te layers grown on GaAs substrates.…”

The Nature and Origin of Lateral Composition Modulations in Short-Period Strained-Layer Superlattices

“…During the growth of alloys, composition modulations may develop for thermodynamic reasons, for example due to phase separation by spinodal decomposition associated with the presence of a miscibility gap e.g. [25,26]. Also, during growth of alloys, composition modulations may develop due to a kinetic instability as described in detail by Ipatova et al [27].…”