Liquid phase epitaxy of unstable alloys: Substrate-induced stabilization and connected effects

Abstract

It is now well admitted that most quaternary III–V compounds show unstable regions in the temperature range commonly used in epitaxy. For instance, according to these authors, the InGaAsP alloy, lattice matched to InP and with emitting wavelength 1.3 μm should be unstable at temperatures below 700 °C. Liquid phase epitaxy, however, is commonly performed down to 600 °C. As this growth technique occurs close to thermodynamical equilibrium, such growth should not take place. It was clearly demonstrated that the substrate stabilizing effect is responsible for this paradoxical behavior. Another LPE substrate effect pointed out by Stringfellow is known as the ‘‘pulling effect.’’ Results will be presented showing the connection between these effects in the system InGaAsP/InP and particularly InGaAs/InP. ‘‘Stabilized’’ GaAsSb was also successfully epitaxially grown on InP, in the immiscibility region, from the liquid phase. Microscopic compositional periodical modulations are observed in standard InGaAsP epilayers, if growths are performed below a critical temperature. This phenomena, also related to solid instability, can be interpreted in terms of liquid–solid interfacial spinodal decomposition.

Epitaxial stabilization of orthorhombic cuprous oxide films on MgO(110)

“…The lack of strain in the film suggests that this metastable phase has a negligible lattice mismatch with the MgO substrate. 18 In the present case, the chemical components are Cu and O. 18 Thus, epitaxial alloy films (e.g., In x ,Ga 1−x As y P 1−y ) grow epitaxially with a composition other than the composition predicted by chemical equilibrium.…”

“…18 Thus, epitaxial alloy films (e.g., In x ,Ga 1−x As y P 1−y ) grow epitaxially with a composition other than the composition predicted by chemical equilibrium. The lack of strain in the film suggests that this metastable phase has a negligible lattice mismatch with the MgO substrate.…”

Thermodynamic theory of epitaxial alloys: first-principles mixed-basis cluster expansion of (In, Ga)N alloy film

“…In the case of a substrate-coherent epitaxial alloy, most of the works [27,36,[39][40][41][42][43] have attempted to account for the epitaxy effect by simply adding the substrate strain energy term to the free energy of the disordered solid solution phase. Consequently, a large depression of miscibility gap temperature has been observed [27,[39][40][41]43]. However, all these models failed to recognize that epitaxial strain could stabilize some ordered structures (i.e., negative formation energies H epi (σ )) and thus convert the bulk phase separation into an epitaxially ordered one [7,8].…”

Numerical Study of InGaN Pattern Formation Caused by Phase Separation

“…15) On the other hand, it is suggested that the phase separation occurs during growth in the case of alloy-semiconductors when the growth condition corresponds to the miscibility gap region. 16) In InGaN-based semiconductor light-emitting devices, after preparing the InGaN active layer at 800 • C, an AlGaN cladding layer is grown at 1000 • C. 1) Thus, atoms on the growing surface of InGaN can easily migrate while the InGaN active layer is exposed to the growth ambient before growth of the AlGaN cladding layer, and the phase separation occurs easily. Hence, we focused the present numerical analysis described in this paper on the process simulation of the phase separation from the growth of the InGaN active layer until that of the AlGaN cladding layer.…”

“…For the heterojunction of lattice-mismatched semiconductors, Quillec et al 16) investigated the contribution of strain energy to the mixing free energy affecting the phase separation. In the case of the InGaN/GaN system, a highly strained InGaN-based SQW or MQW structure is adjacent to the GaN layer as an active layer of a light-emitting device.…”