Study On The Preparation And Characterization Of InN Thin Films By RF-MBE

Microelectronics silicon-based and photonics technology are growing so quickly, in particular the technological limit problem semiconductor technology constantly being proposed,that makes people to explore some new methods such as quantum wires,quantum dots and other new ones,while also continue to explore new semiconductor materials,in order to realize new functions which the existing materials can't achieve.Because of its good electrical properties,InN has a very broad application prospects in the ultra high-speed microelectronic devices,optoelectronic integration and ultra-high frequency microwave devices;especially study in recent years found the band gap of InN is about 0.7eV, making people obtain from 0.7eV to 6.2eV continuous adjustable direct band structures by making through AlGaInN alloy component adjustment,and people can prepare the spectral range from IR to deep UV optoelectronic devices through a single system of semiconductor material,so for InN Materials aroused great interest.But Preparation of InN material is difficult,because the InN dissociation temperature is low,and the growth of the general method requires a very high temperature to Ionize N sources,moreover,difficult to find a suitable substrate material. From the point of the lattice constant and thermal expansion,it is undoubtedly the most attractive to use Si as substrate,and the silicon substrate can make it is achieved for InN devices integrated with Si-based devices.Therefore, this paper will focus on Si-based epitaxial InN thin films and device fabrication.At present,there have been many quite mature technologies in growth InN film, such as magnetron sputtering, halide vapor phase epitaxy, pulsed laser deposition, metal organic chemical vapor deposition and molecular beam epitaxy growth. Molecular beam epitaxy (MBE) technology use directly the metal indium as indium source,N2 or NH3 as the nitrogen source,using the In molecular beam excited and ionized plasma of N in the surface of the substrate to react in order to obtain the InN films.Therefore, people believe that the growth of InN epitaxial film by molecular beam epitaxy is the best choice.In this work,RF-MBE system was used to grow InN epilayer.It is possible to monitor the growth condition by using in-situ surface characterization equipments such as reflection high energy electron diffraction,X-ray photoelectron spectroscopy.Specific studies are as follows:The silicon substrate which had been cleaned with chemical method was put into Analysis Unit annealing for one hour,then placed into the growth chamber to grow epilayer.The first is the optimization of buffer layer.The epitaxial growth of InN films for different Indium source temperature,after scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction instruments we obtained relatively good quality of InN films in the In source temperature of 665℃,all which is crystal growth,but the surface and found no elemental In diffraction peaks;for different substrate temperature growth of InN epitaxial films, through SEM, XPS, XRD and PL spectra characterization means obtained at 420℃we get the best quality crystal,in the end determine the optimal buffer layer growth conditions for the In source temperature was 665℃,the substrate temperature of 420℃,Nitrogen gas flow 350sccm,RF power of 400W,anti-bias power is 3W.Subsequent denotation layer grows on the basis of obtain good buffer layer,by the substrate temperature increased to 465℃and N2 gas flow 450sccm,InN epitaxial thin films obtained with the best quality.Confirmed by X-ray diffraction patterns obtained with only (002) peak and the second order diffraction peak (004) epitaxial thin films, the (002) peak FWHM is 0.1752°,c-axis lattice constant is 0.5709nm; confirmed by scanning electron microscopy, the growth of InN epitaxial films regular shape,are six square,and for the island growth;by atomic force scanning photos can be seen that the root mean square roughness of only 6.29nm.We have a preliminary study of InN/Si heterojunction structure and analysis of its I-V characteristics and their turn-on voltage of 2.01V.The n-InN/p-Si structure is especially attractive due to the well-known advantage of Si substrate (such as low cost and conductive) and its potential application in Si-based optoelectronic integrated circuits.This also indicates that the Si substrate on the production of InN-based optoelectronic devices have broad application prospects.