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To explain different doping effects in a buffer layer, thermally annealed interface, and upper epilayers of GaAs/Si films grown by Metalorganic Chemical Vapor Deposition (MOCVD), the behaviors of unintentional doping in GaAs/Si films are investigated in detail. A third doping mechanism of arsine impurity incorporation during the growth process of GaAs/Si films, apart from conventional mechanisms of gas phase reaction and diffusion from the silicon substrate, is proposed. The experimental results reveal that the doping behavior in the buffer layer studied is determined by the three types of doping mechanisms together. However in the thermally annealed interface and upper epilayers, the third doping mechanism is dominant. According to the third mechanism, the background carrier concentration in GaAs/Si films grown by MOCVD could be properly controlled through the arsine flow rate.

The fabrication of self-catalyzed InP nanowires (NWs) is investigated under different growth conditions. Indium droplets induced by surface reconstruction act as nucleation sites for NW growth. Vertical standing NWs with uniform cross sections are obtained under optimized conditions. It is confirmed that the growth rate of NWs is strongly affected by the surface diffusion adatoms while contributions from the direct impingement of vapor species onto the In droplets can be negligible. The results indicate that the droplet acts as an adatom collector rather than a catalyst. Moreover, the diffusion flow rate of adatoms increases with time at the beginning of growth and stabilizes as the growth proceeds.

Vertical p-type gallium arsenide (GaAs) nanowires with pure zinc blende structure were grown on GaAs (111) B substrate by metal-organic chemical vapor deposition via a Au-catalyst vapor-liquid-solid mechanism. The p-type doping was investigated by additional diethyl zinc (DEZn). In the high II/III ratio range (II/III>9.1%), there exists a critical length beyond which kinking takes place. Two possible reasons are discussed. Zn occurrence in the nanowires was verified by energy dispersive X-ray (EDX) analysis. Corresponding to II/III D 0.2%, the doping concentration is about 8 10 18 cm 3 .

InAs/GaAs and InAs/In xGa1-xAs/GaAs nanowire heterostructures are grown by metal organic chemical vapor deposition via Au-assistant vapor-liquid-solid mechanism. We find that the InAs nanowires grow directly on GaAs nanowires in a random way, or they grow along the sidewall of the GaAs nanowires, and thet InAs nanowires grow vertically on GaAs nanowires by using an In x Ga1-xAs (0≤x≤1) buffer segment. It can be concluded that the influences of crystal lattice mismatch and difference in interfacial energy can be eliminated by inserting a ternary compound semiconductor buffer segment, thereby improving the crystal quality and the capability to control the growth of nanowire heterostructure.

Pure zinc blende GaAs nanowires were grown by metal organic chemical vapor deposition on GaAs (111) B substrates via Au catalyzed vapor-liquid-solid mechanism. We found that the grown nanowires are rod-like in shape and have a pure zinc blende structure; moreover, the growth rate is independent on its diameters. It can be concluded that, direct impingement of vapor species onto the Au-Ga droplets contributes to the growth of the nanowire; in contrast, the adatom diffusion makes little contribution. The results indicate that the droplet acts as a catalyst rather than an adatom collector, larger diameter and high supersatuation in the droplet leads to the pure zinc blende structure of the nanowire.

Pure zinc blende GaAs nanowires were grown by metal organic chemical vapor deposition on GaAs(111)B substrates via Au catalyzed vapor-liquid-solid mechanism. The diameter, size distribution, and density of Au particles can be changed by varying the Au film thickness. We find that the grown nanowires are of rod-like shapes and pure zinc blende structure; moreover, the growth rate depends on the density of Au particles and it is independent of its diameters. It can be concluded that the nanowire was grown with main contributions from the direct impingement of vapor species onto the Au-Ga droplets and contributions from adatom diffusion can be negligible. The results indicate that the droplet acts as a catalyst rather than an adatom collector.

Theoretical expressions of the epitaxial lateral overgrowth rate in the metalorganic chemical vapor deposition (MOCVD) have been formulated in this paper, with respect to two separate processes: vapor phase diffusion and mask surface diffusion. In the case of InP deposition on GaAs substrate, a parametric study was accomplished in order to determine the impact of the mask/window width to the growth rate. The model, which uses a new parameter “effective mask length” Lmask, reveals that the key factors determining the growth rate are mask/window width and mask width/effective mask length. This model can be used as a tool for predict the growth conditions leading to expected growth rate.