Crystal growth and properties of indium phosphide nanowires

The growth, surface chemistry and bulk properties of III-V compound semiconductors and nanowires during metalorganic vapor-phase epitaxy have been investigated. In particular, the following topics were examined in detail: phosphine and tertiarybutylphosphine adsorption on the In-rich indium phosphide (001)-(2x4) surface; annealing of indium gallium arsenide nitride films using nitrogen trifluoride; growth kinetics of indium phosphide nanostructures on indium phosphide (111)B; and the optoelectronic properties of indium phosphide nanowires grown on silicon (111).;Phosphine and tertiarybutylphosphine adsorption on the indium-rich InP (001)-(2x4) surface at 25 °C have been studied by internal reflection infrared spectroscopy, x-ray photoelectron spectroscopy, and low energy electron diffraction. Both molecules form a dative bond to the empty dangling bonds on the In-P heterodimers and the second-layer In-In dimers. The P-H bonds of the adsorbates vibrate symmetrically at 2319 (2315) and 2285 (2281) cm -1 and asymmetrically at 2339 (2339) and 2327 (2323) cm-1 . A fraction of these species dissociate into adsorbed PH2 with the hydrogen and tertiarybutyl ligands transferring to nearby phosphorus sites. The energy barriers for desorption of these molecules is <11 kcal/mol, which is lower than that for dissociation, >17 kcal/mol. This explains the low sticking probability of the group V precursors during InP growth.;The effect of annealing a 75-nm-thick layer of InGaAsN in 1.0x10 -6 Ton of nitrogen trifluoride has been studied by photoluminescence spectrometry, x-ray diffraction, x-ray photoelectron spectroscopy, and hydrogen adsorption infrared spectroscopy. A red shift of 25 nm in the photoluminescence peak was observed following heating in NF3 at 530 °C. The compressive strain of the InGaAsN was reduced under annealing in NF3 ambient, while it increased under annealing in AsH3 ambient. It is concluded that N atoms diffuse into the alloy during the NF3 exposure at 530 °C and increase the nitrogen concentration from about 1.2 to 1.7 %.;Most indium phosphide nanowires are prepared by the vapor-liquid-solid process using gold catalysts. However, gold incorporation into the InP is unavoidable and can adversely affect optoelectronic properties. The growth of indium phosphide nanostructures was investigated without the aid of a foreign catalyst. Instead liquid indium droplets were used to catalyze indium phosphide deposition during metalorganic vapor-phase epitaxy. Three distinct InP nanostructures were observed---wires, cones, and pillars---depending on the substrate temperature. It was shown that the crystal shape depends on the relative rates of indium phosphide deposition via the vapor-liquid-solid and vapor-phase-epitaxial growth mechanisms.;The relationship between crystal quality and the properties of indium phosphide nanowires grown on silicon (111) has been studied by transmission electron microscopy, photoluminescence spectroscopy, and photoelectrochemistry. Wires with no defects and with {111} twin boundaries parallel and perpendicular to the growth direction were obtained by metalorganic vapor-phase epitaxy using liquid indium catalyst. Room temperature photoluminescence from the defect-free nanowires is ∼20 times more intense than that from the wires with twin boundaries. Photoelectrochemical experiments reveal that the open-circuit photovoltage of defect-free wires is substantially greater than those with twins. In summary, twin boundaries strongly affect the optoelectronic properties of InP nanowires.