The Characteristics Of Gan Films Deposited On Ti Coated On Glass Substrates With ECR-PEMOCVD At Low-temperature

Gallium nitride (GaN) is considered to be an attractive semiconductor for its wide band gap and wurtzite structure. The band gap is about4.39eV. The direct band gap makes it be suitable for light emitting diodes (LEDs) and laser diodes (LDs). Furthermore, the excellent thermal stability of GaN also makes it to be a promising material for high-temperature and high-power semiconductor devices. However, bulk GaN crystals are not commercially available, most researchers have relied on heteroepitaxy, which is crystal deposited on substrates of another material for device fabrication. Sapphire is the most common substrate for GaN epitaxy, but there are many disadvantages for sapphire to be a substrate. It is electrically insulating material and has a low thermal conductivity. The performance of GaN devices, especially high power, is often restricted by the poor electric conductivity and the low thermal conductivity of the sapphire substrate. On the contrary, metal is an ideal conductor of electricity and heat.There are several reports on the use of copper and silver as substrates to epitaxial growth GaN films. However, the conventional growth techniques need high growth temperature, which lead to serious interfacial reactions between GaN films and metal substrates. In order to solve this problem, GaN films were grown using electron cyclotron resonance plasma enhanced metal organic chemical vapour deposition (ECR-PEMOCVD) system at low temperature in our previous report. This system deposites GaN films by ECR technology at low temperature.In this article, highly c-axis-oriented GaN films are deposited on Ti film. Trimethyl gallium (TMGa) was used as the source of gallium, N2was used as the source of nitrogen. The influences of TMGa flux and nitriding time on the properties of GaN films were systematically investigated. The test equipment include reflection high energy electron diffraction(RHEED), atomic force microscopy(AFM), photoluminescence spectra, X-ray diffraction analysis(XRD),Raman scattering and Current-voltage characteristic. The GaN film with small surface roughness and high c-axis preferred orientation was successfully achieved at the optimized TMGa flux of1.0seem, nitriding time of20min, N2flux of100seem and the substrate temperature of380℃.