The Synthesis Of One-dimensional GaN Nanostructure And GaN Film By CVD

GaN is an excellent wide band gap III—V compound semiconductor material and also one of the best advanced semiconductor materials. Having large direct energy band gap of 3.4 eV at room temperature, GaN is an ideal material for fabricating optoelectronic devices, especially blue and green light emitting diodes (LEDs) and laser diodes (LDs). This kind of materials have good potential application and great market demand in high density optical information memory, high speed laser print, high brightness dynamic, full color display, solid illumination, signal detector and communication. In addition, GaN attracts much attention for fabrication of high temperature, high frequency and high power devices. Presently, much attention is being paid to GaN materials all over the world. MOCVD, MBE, and HVPE have become dominating methods for growing GaN. Among these techniques, MOCVD has been widely used by researchers. However, GaN materials are not well prepared and applied in large scale because of the complicated growth technics and expensive equipments by above methods. Now, a lot of scientific research institutions are exploring new technique to grow high quality GaN film on appropriate wafer. For recently years, one-dimensional GaN nanostructure has gained considerable attention for its potential application both in visible light and ultraviolet light optoelectronic devices, one-dimensional GaN materials have become a worldwide focus.In this paper, high purity one-dimensional GaN structure and GaN film were synthesized on Si wafer by CVD, its composition and structure were analyzed, the growth mechanism and influencing factors of one-dimensional GaN growth were discussed.1. GaN nanobelts were synthesized by direct reaction of metallic gallium with flowing ammonia using physical evaporating Ni as catalyst on Si substrate via CVD at 950℃. Results indicated that as-synthesized nanobelts were single crystalline, hexagonal wurtzite structure GaN. Its widths were in the range of 50-200 nm, with the ratio of thickness to width to be about 1/20 and their lengths up to several tens of microns. The nommiformity radial growth was assumed to lead to beltlike nanostructure. The catalytic growth mechanism of GaN nanobelts was probably dominated by conventional VLS mechanism.2. Hexagonal cone-shaped GaN nanostructure were synthesized by direct reaction of metallic gallium with flowing ammonia using physical evaporating Ni as catalyst on Si substrate via CVD at 1050℃. Results indicated that as-synthesized structure were single crystalline, hexagonal wurtzite structure GaN. Its mean diameter is about 500 nm, with the lengths several microns. Its growth mechanism was probably dominated by conventional VLS and VS mechanism.3. GaN nanowires were synthesized by direct reaction of metallic gallium with flowing ammonia using electric plating Ni as catalyst on Si substrate via CVD. Results indicated that as-synthesized nanowires were curved, and had smooth surface. Its diameters were in the range of 20-100 nm, with the lengths several tens of microns. Its growth mechanism was probably dominated by conventional VLS mechanism.4. Zigzag GaN nanowires were synthesized by direct reaction of metallic gallium with flowing ammonia on Si substrate by CVD. Results indicated that as-synthesized nanowires were not smoother than nanowires as-synthesized using Ni as catalyst. Its diameters were in the range of 30-150 nm, with the lengths several tens of microns. Its growth mechanism was probably dominated by conventional VS mechanism.5. It was found that substrate surface is an important factor affecting product morphology. It is easy to form nanowires on smooth surface and form nanobelts on rough surface. However, the relationship between the smooth degree of substrate and product morphology has not been clear, which needs further investigation. And heating rate is also an important factor affecting product morphology, it was found that it is easy to form nanowire or nanobelt structure with high heating rate and form film morphology with low heating rate.6. GaN film and other morphologies such as nanobelt ring, nanorod, and nanosheet were also synthesized.