Papers by Keyword: Gallium Phosphide

Abstract: Gallium Phosphide (GaP) nanostructures were grown on p-Si substrates by Metal Organic Chemical Vapor Deposition (MOCVD) to study the structure of low dimensional IIIV semiconductor on Si substrates. It is found that at a temperature of 540 °C, nanostructures with diameter 4080 nm and height 515 nm were obtained. The density of the nanostructures was found to be 10¹⁴ m^-2. The UV-Vis-NIR spectra showed a blue shift of band gap. Photoluminescence measurements also confirmed the band gap enhancement.

Abstract: We study the initial growth of 10 monolayers (MLs) of GaSb on a (001) GaP substrate. Transmission electron microscopy and reflection high energy electron diffraction analysis show that an Sb-rich GaP surface promotes the formation of a 90° misfit dislocation array at the epi-substrate interface. Using atomic force microscopy, we investigate the influence of the growth temperature and the growth rate on the formation and the shape of GaSb islands.

Abstract: A brief history of visible light-emitting diodes (LED's) is given, from the first experimental observations of H.J.Round in 1907 to the mid-1970's when red and green emitters were in extensive production. Early investigations were empirical. This was changed with the invention of the transistor in 1947 by the demonstration of minority carrier injection at a forwardbiased junction, followed by recombination. In 1952 the discovery of the semiconducting behaviour of III-V compounds introduced a new range of materials. Gallium nitride seemed attractive for light emission and was investigated at Philips and RCA laboratories but at the time proved to be too difficult for practical use. Gallium phosphide emerged as the most promising material and groups to investigate it were set up at SERL in England, Philips Central Research Laboratories in Germany and Bell Telephone Laboratories in the USA. Zinc and oxygen doping gave red emission. At Philips, the emphasis was on efficiencies. At SERL the emphasis was on reproducibility for manufacturable devices and when the conditions for zinc and oxygen doping were strictly controlled the world's first practical visible LED's were produced at the end of 1961. At Bell Telephone Laboratories progress was initially slow but with the advent of liquid-phase epitaxial growth production of red emitters on the scale required became possible. The accidental discovery of nitrogen doping of gallium phosphide at Bell led to the production of good green emitters. Until the end of the 1970's, gallium phosphide red and green emitters dominated the LED market. Subsequent developments to the present day are sketched in outline.

Abstract: High purity nanowires are successfully synthesized by chemical vapor deposition. In this work, we have tried synthesis of GaP nanowires with copper oxide catalyst using chemical vapor deposition method involving a metal oxide-assisted vapor-liquid-solid (VLS) growth mechanism. The synthesis process is the same as that described in existing work except for a catalyst. The mixture of GaP and Ga powder was used as GaP source for synthesis of GaP nanowires. And the mixture powder was directly vaporized in the range of 700~1000°C under argon ambient in a furnace. The wire-like products was observed in the range of 800~950°C. The diameter of nanowires increases with increasing synthesis temperature, but reversely, the length of nanowires decreases steadily. The nanowires prepared at 850°C possess perfect wire-like shape and uniform distribution of diameter. The average diameter and length of nanowires are about 50
 and 150, respectively. HRTEM and EDX analysis were carried out to obtain more detailed information of its microstructure. Nevertheless, all condition of processing was set for making the high purity GaP nanowires as existing reported method, the nanowires were identified as well-crystallized gallium oxide nanowires with an amorphous outer layer. It does not accord with existing reported results. This result means that the catalysts play a key role in the growth of nanowires.

Abstract: Gallium phosphide nanowires were successfully synthesized by the catalytic chemical vapor deposition (CVD) method using MgO powder-impregnated nickel oxide as catalyst and gallium phosphide and gallium powders as GaP source. The synthesis of GaP nanowires were carried out at 900°C for 30min under argon ambient and directly vaporized Ga and GaP powder. The diameter of GaP nanowires is about 25~70nm and the length is up to several tens of micrometers. The GaP NWs was core-shell structure, which consists of the GaP core and the Ga oxide outer layers. The GaP nanowires have a single-crystalline zinc blend structured crystals with the [111] growth direction. Nanowires larger than around 50nm in diameter exhibited twinning faults, which appears in the TEM images as discrete dark lines and alternating wire contrast. We demonstrate that MgO powder-impregnated nickel oxide catalyst exhibited a large catalytic effect on the growth of high-purity and -quantity gallium phosphide(GaP).

Abstract: Long-wave infrared windows and domes used under harsh conditions always suffer sand abrasion and raindrop erosion. GaP thin film has proved to be effective LWIR protective coating for zinc sulphide window. In this article, the GaP films have been deposited on 5-mm-thick thermo-pressed planar ZnS substrates by RF magnetron sputtering in high pure Ar gas, with a single crystalline GaP disc as the target. The maxima of the GaP/ZnS transmission spectra curve are less than the corresponding transmissivities of ZnS substrates, which indicates that the GaP films are of absorption. SEM results show that the films are very compact and their surfaces are glazed. XPS analysis shows that gallium content is more than phosphor content in the films, and oxygen is the main impurity. The more the gallium content is, the more absorption the film is of. The absorption does not vary greatly with oxygen content. So the absorption of the film is caused mainly by the overfull metal component, which increases the conductivity and causes the charge carrier absorption. Low absorption GaP film with the thickness more than 10 µm has been deposited, in which the Ga:P ratio is nearly 1:1.