Preparation Of Hexagonal Ga₂O₃ Film And Characterization Of Nitridation And Doping Ga₂O₃ Film

Semiconductor materials in all areas of information technology have a wide range of applications in the semiconductor device on the basis of their preparation,which is gradually improving human life. With the continuous development of the information age, there is an urgent need to find new semiconductor materials to meet the development of technology, then, the oxide semiconductor materials cause people's study Ga₂O₃, as a representative of the new oxide semiconductor material, attracted widespread many scholars'attention in recent years. Ga₂O₃ is a compact wide direct band gap semiconductor material, showing five different crystal structures, namely ?-Ga₂O₃, ?-Ga₂O₃, y?-Ga₂O₃,?-Ga₂O₃ and ?-Ga₂O₃ five kinds of structure, wherein the monoclinic ?-Ga₂O₃ is the most stable crystal structure. Because Ga₂O₃ band gap lies in 4.2-4.9eV, and has its excellent chemical and thermal stability, it has a more extensive application in the area of ultraviolet detectors, field effect transistors, transparent conductive films. Ga₂O₃ film preparation methods are commonly used:a magnetron sputtering method, MBE, metal organic compound vapor deposition ?MOCVD? and other methods. There are more current reports on technical methods of ?-Ga₂O₃ material epitaxially growth, and less reports on other crystal structure. Based on the above background, this paper carried out a study of the growth and characteristics of ?-Ga₂O₃ material. We use MOCVD technology method to grow ?-Ga₂O₃ film on 6H-SiC and sapphire substrate respectively,then we put them in different atmosphere N2 and NH3 for the heat treatment, and systematically study the changes of crystal structure before and after the heat treatment of the film, the epitaxial relationship,the surface morphology and other properties.The main contents and results of this paper are as follows:?1? Study the effect of different annealing temperature on the crystal structure of ?-Ga₂O₃ films and surface morphology, we use MOCVD equipment,with high purity TEGa as Ga source, high purity O2 as an oxygen source, Ar as a carrier gas, to grow ?-Ga₂O₃ film in on 6H-SiC substrate at temperature of 500 ?.then we anneal ?-Ga₂O₃ film in N2 atmosphere for 30mins at different temperatures 800 ?,850?,900 ?. We use X-ray diffraction ?XRD?, scanning electron microscopy ?SEM?, atomic force microscopy ?AFM? to test the samples. The XRD analysis results of the samples at different annealing temperatures showed ?-Ga₂O₃ films at annealing temperature 850? starts to change into ?-Ga₂O₃, and at annealing temperature 900?,the sample has been completely transformed into ?-Ga₂O₃.The thermal stability of ?-Ga₂O₃ film can be maintained at about 800 ?.From high-resolution X-ray diffraction test results,we can achieve the epitaxial relationship of the inner surface ?-Ga₂O₃ ?1120?//6H-SiC ?1120? and the epitaxial relationship of outer surface ?-Ga₂O₃ ?0001?// 6H-SiC ?0001? between ?-Ga₂O₃ film and 6H-SiC substrate. From the analysis results of SEM image,we can obtain ?-Ga₂O₃ film surface is smooth and continuous and thermal stability of ?-Ga₂O₃ film is maintained at about 800?, surface roughness of the samples show a trend from increase to reduce. The analysis results AFM are consistent with the test results of SEM.?2? Study the changes of crystal structure and the component of ?-Ga₂O₃ film before and after the nitriding treatment. We utilize the same process conditions above to grow ?-Ga₂O₃ film on sapphire substrate, and then we anneal ?-Ga₂O₃ film in NH3 atmosphere for 30mins. We analyse two groups of samples with many test methods XRD, scanning electron microscopy ?SEM?. We can obtaine from the XRD results after nitriding treatment,that the sample surface has formed the GaN film, having the characteristics of the C-axis preferred orientation. From the SEM image,?-Ga₂O₃ film surface after nitriding treatment has the formation GaN crystal. Transmission spectrum test results showed the samples treated surface nitriding has a very distinct light absorption phenomenon at 365nm position ?GaN film intrinsic absorption edge?, indicating that ?-Ga₂O₃ film surface has the formation of GaN crystal. Derived from the XPS results? using metal organic chemical vapor deposition ?MOCVD? technology, high purity triethyl gallium ?TEGa? as a gallium source,diethyl zinc ?DEZn? as a doping source of zinc,high purity oxygen ?99.995%? as an oxygen source,high-purity argon ?99.999%? as a carrier gas,three groups of Zn-doped gallium oxide films were deposited under different Zn flow 0.36,0.72,0.144?mol/min.Using a thin film thickness analyzer,X-ray diffraction and UV-visible double-beam spectrophotometer to test samples thickness,analyze the crystal structure and optical propertie of samples.Using the method of thermal evaporation to make titanium and aluminum electrodes on the surface of gallium oxide.The electrical properties of samples were characterized by ?-? test.Related test results showed that the crystalline and optical quality gallium oxide film increased with Zn source flow increasing.Zn source flow reached 1.44?mol/min,single orientation of ? phase gallium oxide film had steep UV absorption edge.The optical band gap was 4.93eV and average transmittance in the visible range ?350-800nm? was higher than 97%. However,Zn-doped gallium oxide film conductivity reduced with Zn source flow increasing,because Zn atom didn't play a significant role in the donor or acceptor, And the crystal quality of gallium oxide film increased with the increase of Zn source so that the relevant inherent defect density having conductive property reduced.