Low-temperature Growth And Characteristic Analysis Of GaN Films On Glass Substrate

As a member ofâ…¢/â…¤nitrides family, GaN is direct wide-band gap semiconductor with wurtzite crystal structural and band gap of 3.39eV at room temperature, which is a new generation semiconductor material and has a wide application in future. Then GaN can be made into photonic devices such as blue-green lighting emission diode (LED) and laser diode (LD) with high efficiency and so on. Meanwhile GaN-based semiconductor materials have super properties, such as high electron saturation drift velocity, high thermal conductivity, good chemical, thermal stability and so on, so they are also suitable for manufacturing high-temperature, high-frequency, high-power microelectronic devices, for example, GaN-based field effect transistor (FET) device, GaN-based heterostructure field effect transistor (HFET) and so on. However, due to lacking of substrate material with bulk single crystal,α-Al₂O₃ or SiC is mostly used as substrate for heteroepitaxial GaN at present. But it has shortages of small size no more than 50mm and high cost. In 2007, the BluGlass group in Australia has discovered that GaN film deposited on the diameter of 150mm glass emitted blue light, it means high quality LED material can be deposited on the large area glass substrates and the cost of LED can be droped remarkablely. Conventional glass substrate is a preferred candidate materials for commercial application of photonic devices with large-area and low-cost.Low-cost and large-area fabrication can be realized if GaN film is successfully deposited on glass substrate. For practice applications, it is necessary to deposit high quality poly-GaN film at low temperature on cheap substrates such as noncrystalline glass.Nowadays we can mainly use physical and chemical methods to deposit GaN films. Physical methods include evaporation and sputtering; Chemical methods mainly include molecule beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE) and so on. In these methods, MOCVD is more suitable for large-scale industrial production, and attracts more and more people's attention, because it has the advantages of the simple experimental parameters, the mature technology, the high quality of films deposited.C-axis oriented GaN films are deposited directly on CONING 7101 glass substrates by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) at a low temperature using Trimethyl-gallium (TMGa), High purity N₂ and H₂ as N sources and carrier gas of Ga respectively. The use of microwave ECR to produce plasma in the low pressure maked it easy to decomposite N₂ and greatly decreased the deposition temperature in the experiment. In addition, we can not use too high temperature in the experiment because of the relatively low melting point (<600℃) of glass. The effects of deposition temperature, N₂ flow rate andâ…¤/â…¢ratio on the film structrue, surface morphology, electrical properties and optical properties of GaN films are investigated by use of reflection high energy electron diffraction (RHEED) in situ, X-ray diffraction (XRD), atomic force microscope (AFM), Hall measurements and room temperature photoluminescence (PL) spectra. The suitable processing parameters of GaN deposition on the glass have got in our experiment.