The structural and optical properties of GaAs1−xBix alloys for x up to 0.108 have been investigated by high resolution X‐ray diffraction and photoluminescence (PL). At room temperature (RT), the PL intensity of the GaAs0.97Bi0.03 sample was found to be ∼300 times higher than a GaAs control sample grown at the same temperature (400 °C). PL measurements carried out at 10 K show that when excitation power, Pex was increased from 0.11 to 1140 W cm−2, the PL peak energy blue‐shifts by 80 meV while the full‐width‐at‐half‐maximum reduces from 115 to 63 meV. However, the PL peak emission energy becomes independent of the excitation power at RT. The results indicate the presence of localized energy states in the GaAs0.97Bi0.03 sample, which trap carriers at low temperatures and that the majority of the carriers become delocalized at RT. Furthermore, the temperature dependent PL also shows an S‐shape behavior, which is a signature of localization effects. A theoretical model, which was derived by solving a rate equation was employed. The model successfully reproduces the observed S‐shape behavior and the theory fits well with the experimental data. The RT band gap of GaAs1−xBix for x up to 0.108 has been plotted and compared with the literature.

GaAs1−xBix alloys grown by molecular beam epitaxy for x up to 0.06 were studied by photoluminescence (PL). The results indicate that dilute fractions of bismuth (Bi) with x < 0.025 improve the material quality of this low temperature growth alloys by reducing the density of gallium (Ga) and/or arsenic related defects. The crystal quality starts to degrade at higher Bi concentration probably due to significant amount of Bi-related defects, BiGa. However, the room temperature PL intensity continues to increase with Bi content for the range studied due to greater band-gap offset between GaAs and GaAs1−xBix. Analysis carried out shows no correlation between localization effects and the room temperature PL enhancement.

For the Ga-assisted growth of GaAs nanowires on Si(111) substrates by molecular beam epitaxy, growth temperature, As flux, and Ga flux have been systematically varied across the entire window of growth conditions that result in the formation of nanowires. A range of GaAs structures was observed, progressing from pure Ga droplets under negligible As flux through horizontal nanowires, tilted nanowires, vertical nanowires, and nanowires without droplets to crystallites as the As flux was increased. Quantitative analysis of the resulting sample morphology was performed in terms of nanowire number and volume density, number yield and volume yield of vertical nanowires, diameter, length, as well as the number and volume density of parasitic growth. The result is a growth map that comprehensively describes all nanowire and parasitic growth morphologies and hence enables growth of nanowire samples in a predictive manner. Further analysis indicates the combination of global Ga flux and growth temperature determines the total density of all objects, whereas the global As/Ga flux ratio independently determines the resultant sample morphology. Several dependencies observed here imply that all objects present on the substrate surface, i.e. both nanowires and parasitic structures, originate from Ga droplets.

Studies on atomic layer deposition Al2O3/In0.53Ga0.47As interface formation mechanism based on air-gap capacitance-voltage method Appl. Phys. Lett. 101, 122102 (2012) A mathematical model for void evolution in silicon by helium implantation and subsequent annealing process J. Appl. Phys. 112, 064302 (2012) Void evolution in silicon under inert and dry oxidizing ambient annealing and the role of a Si1−xGex epilayer cap

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