The Characteristics Of InN Films Deposited With ECR-PEMOCVD At Low Temperature

Indium nitride (InN) is an important III nitrides semiconductor material with direct narrow-band gap (the exact band-gap of0.7eV at room temperature). It has the smallest effective mass, the highest carrier mobility and electron saturation drift velocity comparing with other III nitrides semiconductor materials including gallium nitride (GaN) and aluminum nitride (A1N). The low field mobility and peak drift velocity in InN at300K is about3200cm2/V?s and4.3X107cm/s. These characters of InN proved the unique benefits of high frequency centimeter and millimeter wave application. The current commonly quoted band gap value for InN is corrected from1.89eV to0.7eV at room temperature, so this character makes the emission wavelength of III nitrides semiconductor materials extending from red wavelength (InN,0.7eV) to ultraviolet wavelength (A1N,6.2eV). Considering the potential application of the alloy of InN (InGaN) in solar cell, the full spectrum solar cell becomes the hot research spot. The preparation of the solar cell requires large area and cheap substrate materials. But the common epitaxial substrates (α-Al2O3and SiC) of the growth of GaN, InN and InGaN films make high cost substrates and become the barrier of the further development of solar cell. Due to the features of the mature process, low cost and large area preparation of glasses as the suitable substrates, cost reduction and large area preparation come true. But the softening temperature of common glasses is at600, and higher temperature would make the impurities of glasses diffusing into the epitaxial films. This would cause involuntary doping. However, the deposition temperature of the usual Metal Organic Chemical Vapor Deposition (MOCVD) is above800°C, so it is hard to use glasses as the substrates.We carried out the experiment by the Electron Cyclotron Resonance-Plasma Enhanced Metal Organic Chemical Vapor Deposition (ECR-PEMOCVD) with in-situ Reflection High Energy Electron Diffraction (RHEED). ECR-PEMOCVD integrates the advanced technology between MOCVD and MBE. It will produce high density charges and ions by the discharge of Electron cyclotron resonance (ECR) in the low pressure make it easy to produce chemical reaction with low temperature. It’s very suitable to grow semiconductor films with low temperature on the glass substrates and nitrogen as the nitrogen source. That can control the temperature under600°C. ECR-PEMOCVD also can realize the real-time observation of surface microstructure information by RHEED.Our work is to prepare AZO (ZnO:Al) films with high c-axis preferred orientation on the glass substrates by RF magnetron sputtering and then use two steps to grow c-axis (002) oriented InN films on the AZO interlayers on glass substrates by ECR-PEMOCVD with Trimethyl-Indium (TMIn) as the In source and high purity N2employed as the nitrogen source. Study epitaxial films’crystallinity, surface topography and optical properties with analytical techniques as RHEED, X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission and reflection spectra when different deposition temperature and TMIn flux carried out. Finally, we found out the optimum condition of the growth of InN films and the deposition temperature. TMIn flux influence directly the epitaxial growth of InN films and the conditions of growth are narrow. Moreover, AZO films as the buffer layer is effective to the epitaxial growth of InN films to improve their crystallinity with transmitting the information on c-axis orientation (002) from AZO films to InN films. The results show good crystal quality when the TMIn flux is5.5sccm and the deposition temperature is450°C with other parameters unchanged.