III-V alloy decomposition during epitaxy: Ion-assisted growth of indium gallium arsenic antimonide Monte Carlo modeling of immiscible alloys.

摘要

The role of ion-surface interactions in suppressing decomposition in immiscible III-V alloys was investigated. In{dollar}sb{lcub}rm x{rcub}{dollar}Ga{dollar}sb{lcub}rm 1-x{rcub}{dollar}As{dollar}sb{lcub}rm y{rcub}{dollar}Sb{dollar}sb{lcub}rm 1-y{rcub}{dollar} alloy films across the miscibility gap were deposited using an ion-assisted deposition (IAD) chamber designed to provide very-low-energy ({dollar}<{dollar}30 eV), high flux ({dollar}sim{dollar}0.5 mA/cm{dollar}sp2{dollar}) Ar-ion irradiation during growth.; Broadened and split X-ray diffraction (XRD) peaks, and increased surface roughness was observed in InGaAsSb films as a function of the proximity of the alloy composition to the center of the miscibility gap. Immiscible InGaAsSb films, grown nearly lattice-matched on InP (001) substrates, were analyzed using cross-sectional transmission electron microscopy (XTEM), and transmission electron diffraction (TED). A columnar decomposition morphology along the growth direction with a composition modulation wavelength of {dollar}sim{dollar}5 nm was observed. The evidence indicated rapid spinodal decomposition by surface diffusion during vapor phase deposition.; During ion-assisted growth, the alloy structure and properties were strongly dependent upon the energy, E{dollar}sb{lcub}rm i{rcub}{dollar}, of Ar ions bombarding the growing film. An optimum E{dollar}sb{lcub}rm i{rcub}{dollar} range of 19-21 eV was found to yield suppressed composition modulation, single sharp XRD peaks, and increased electron mobility. E{dollar}sb{lcub}rm i{rcub}{dollar} range {dollar}ge{dollar} 22 eV resulted in extensive ion-damage.; The Monte Carlo technique was used to simulate the vapor phase epitaxy of III-V binary alloys, and the IAD of immiscible ternary alloys on (001)-oriented substrates. Simulation results predicted that spinodal decomposition at the film surface during growth can lead to a decomposition morphology similar to that experimentally observed. Simulations of the growth of immiscible alloys using ion bombardment also demonstrated that significant increases in alloy homogeneity can be expected for reasonable ion-to-deposited atom ratios ({dollar}>{dollar}10) when E{dollar}sb{lcub}rm i{rcub}{dollar} {dollar}ge{dollar} 16 eV. A collisional ion-mixing mechanism was shown to be responsible for the suppression of composition modulation in decomposed alloys.