Metalorganic vapor phase epitaxy of III-V heteroepitaxial systems: Investigation of structural and chemical effects of lattice strain

The heteroepitaxial growth of III-V semiconductor materials was studied using metalorganic vapor phase epitaxy (MOVPE). The lattice-mismatch derived strain and subsequent strain-relaxation during the growth of heteroepitaxial films can lead to structural and compositional changes in the material. The strain-related structural effects were studied within the InAs/GaAs heteroepitaxial system, whereas strain-related compositional effects were evaluated for the GaAs1-ySby/GaAs system.;The large lattice mismatch (7%) between InAs and GaAs leads to a complex microstructure with many misfit-derived defects. The dependence of the microstructure and morphology of InAs films, deposited on (100) GaAs substrates on growth parameters and the substrate miscutwas studied. At high growth temperatures and high V/III ratios, multiple tilting of the InAs crystal lattice resulted in domains misoriented by 4-7° with respect to each other. This microscopic tilting of InAs films was attributed to the tilting of lattice planes within large-size (> 1 μm) islands. Low growth temperatures or low V/III ratios resulted in a singly-oriented InAs film aligned with the GaAs. The early coalescence of smaller islands at low growth temperature resulted in a single InAs orientation in the coalesced films. The observed effects were discussed in terms of the effect of an In-rich growth environment, resulting from the low growth temperature and low V/III ratio, on the InAs growth chemistry and the strain relaxation phenomena.;The strain-induced 'lattice-latching' and Sb-surface segregation effects can limit the Sb-mole fractions in the pseudomorphically-strained GaAs 1-ySby layers. The Sb-incorporation efficiency in relaxed and strained GaAs1-ySby films showed a strong dependence on the choice of Ga- and Sb- precursor chemistry and the growth temperature. The Sb-mole fraction in the GaAs1-ySby films decreased with increasing As/Ga-precursor ratio. The Sb-mole fraction in the strained GaAs1-ySby films was found to be lower than that in the relaxed films for all the precursor chemistries. The strained-layer Sb-mole fraction was higher for the trimethyl gallium (TEGa)-chemistries compared to trimethyl gallium (TMGa)-chemistries, due to the rapid gas-phase decomposition of TEGa to elemental Ga. The changes in composition and structure of the MOVPE-grown heteroepitaxial films were attributed to the interplay of chemical kinetics, temperature and strain.