Molecular Beam Eitaxy Grwoth And Materials Studies Of InGaN Nanorod Arrays

Gallium nitride and its alloys (AlGaInN) are important wide bandgap materials used in optoelectronics and high-power, high-temperature, and high-speed electronics. Single crystalline GaN nanowire or nanorod arrays have been investigated and have shown great potential in high electron mobility transistor, light emitting diode, solar cells, and heterojunction diodes. However, the mechanism for the growth of InGaN nanorods by MBE still remains unclear and there are few reports concerning with the growth mechanism. It has been reported that the adatoms diffuse to the nanorod apex from its lateral driven to a lower chemical potential at the top surface. This diffusion-induced mechanism can be used to explain the observed length dependence on diameter for deposition time longer than the nucleation time. In fact, for a complete understanding of the growth mechanism, the nucleation process is very important. Recent investigations suggested growth modes including the nucleation process, but without any direct evidence. Thus, it is necessary to find evidence to conform the growth mechanism. Recently, nanowire or nanarod arrays of GaN and its alloys have been synthesized on Si substrates, since the heterostructures of them are of particular interest for the combination the advantages ofⅢ-nitrides and Si substrates. InGaN with a bandgap from 0.7 to 3.4 eV has attracted considerable interest during the past years and has been considered as the most important and indispensable material for the fabrication of light emitters working in whole visible and part of the near ultraviolet spectral regions. Therefore, synthesis of well-aligned InGaN nanorod arrays on Si substrates is highly demanded. As a principal technique for growth of device-quality InGaN nanorods and thin films, molecular beam epitaxy offers advantages of growth of sharp interfaces for heterostructures, arguably representing the most important method for the controllable growth of device structures. The main results are summarized as follows: 1、Well aligned InGaN nanorod arrays were synthesized on sapphire substrates. The growth mechanism was confirmed by in situ reflection high energy electron diffraction, optical reflective spectrum and ex situ field-emission scanning electron microscope (FESEM) observations.A model was proposed based on these.2、High temperature AIN buffer layer was used to grow well aligned InGaN nanorods on Si substrates.The PL intensity of the AIN-buffered InGaN nanorods is 57 times higher than that directly grown on Si substrates.The apitaxy relations of them were studied.3、We have fabricated n-InGaN/P-Si hetero-structures, which exhibit well rectifying behavior with a low turn on voltage, energy band diagram of the heterostructure was studied to explain this.