The Characteristic Of ECR Plasma And Its Application In Deposition Of GaN Thin Film

With the development of optoelectronic material from GaAs to new generation GaN-based semiconductor material, how to manufacture long-life, high light-emitting and low power -consuming optoelectronic thin film has been a main topic in current optoelectronic material industry. At present the prevailing epitaxial growth techniques of GaN are Metalorganic Chemical Vapor Deposition (MOCVD), Molecule Beam Epitaxy (MBE) as well as HVPE. However, all of them had the same insuperable problem that the epitaxy of GaN thin film had to be happened in high temperature no less than 1000 C. As a result, impurity as well as structure defect will be induced.To overcome the bottle-neck, Electron Cyclotron Resonance - Plasma Enhanced Metalorganic Chemical Vapor Deposition was developed. ECR- PEMOCVD has an incomparable property that the growth of high quality GaN thin film can be controlled in a low range of temperature from 400 C to 600 C. Accordingly, the structure defect and thermal mismatch will be reduced .The gas sources that we used are trimethylgallium (TMG) and 99.9999% purity nitrogen, which were fed into reaction chamber and resonance cavity respectively. The highly dense ECR plasma up to 1011cm-3 was created in the resonance cavity and introduced to the next reaction chamber by the force of divergent magnetic field. Consequently, GaN thin film was grew on the substrate sapphire (0001) placed in the downstream.Single Langmuir probe was adopted to measure distribution of the ECR plasma in the reaction chamber in order to obtain the appropriate deposition condition. During the deposition processes, the heating temperature and other parameters were changed step by step to get the perfect growth condition of GaN film.The crystal quality of GaN was finally investigated by XRD and FTIR. The result of XRD showed that the peak of GaN(0002) at 2=34.752 had a fine 18' of FWHM under the condition of TMG:N2=1:5, PW=550W, P=0.1Pa and T=450 C. The film thickness was 3.5 m and the growth rate was up to 2 m/h according to the interference pattern in infrared reflectance(IR) spectrum. All of the results implied that the ECR-PEMOCVD had an excellent advantage in deposition of GaN film or other films which otherwise should be synthesized in high temperature.