Low‐temperature phase diagram of the Ga‐As‐Sb system and liquid‐phase‐epitaxial growth of lattice‐matched GaAsSb on (100) InAs substrates

摘要

The liquidus and solidus in the Ga‐rich corner of the Ga‐As‐Sb system were determined by experiments using liquids of constant antimony concentration xLSb =0.0615. Evidence was obtained for a quite asymmetric solid‐phase miscibility gap. A theoretical phase diagram has been calculated on the basis of simple solution model. This diagram predicts the equilibrium conditions for the liquid‐phase epitaxy of lattice‐matched ternary layers on InAs substrates in the growth temperature domain 500–600 °C, but it gives a symmetric solid‐phase miscibility gap that is inconsistent with our experimental data. The actual conditions for exact lattice matching were experimentally determined by measurements on liquid‐phase‐epitaxial layers grown by the supercooling method on (100)‐oriented InAs. Flat and uniform mirrorlike epilayers were obtained using slight initial supercoolings (3–10 °C) within the range of relative lattice mismatch from -0.05% to +0.1%, which corresponds to positive mismatch (alayer≫asubstrate) at the growth temperature (∼550 °C). The growth kinetics of the lattice‐matched ternary alloy, which has the composition GaAs0.09Sb0.91, appear to be governed by solute diffusion in the liquid. If it is assumed that As and Sb have the same diffusion coefficient, a value of 6.8×10-5 cm2 s-1 for this coefficient is obtained by fitting the experimental data.