Growth Of Antimony-doped ZnO Thin Films By MOCVD Technique And Investigation On Its Optical And Electrical Properties

Zinc oxide is a direct and wide bandgap semiconductor material with many promising properties for blue/UV optoelectronics. For ZnO, its exciton binding energy is 60 meV and it has direct bandgap energy of 3.37 eV at room temperature. The electron Hall mobility in single crystal ZnO is 200cm2V-1-s-1 (RT). Due to zinc oxide's prospects in optoelectronics applications, it has become a promising material for fabrication of the electronic devices operating in the blue-violet and near-UV spectral range with low threshold and high efficiency character at RT and beyond. Currently, the key factor that has long been the bottleneck of ZnO based light-emitting diode and lasing diode is the realization of stable and reproducible high quality p-type ZnO thin films. In this thesis, the author conducted many research works to resolve the issue above. The antimony-doped ZnO thin films were deposited on c-plane sapphire substrates by MOCVD technique. The author's research works contain mainly two parts which were described as follows:(1) To investigate the influence of different substrate temperatures on the ZnO thin film growth, the antimony-doped ZnO thin films were deposited on c-plane sapphire substrates at 500℃,550℃and 600℃by MOCVD technique. The samples were investigated by X-ray diffraction, Hall effect measurement and photoluminescence (PL) spectrum measurement. The results of XRD indicate that the crystalline quality of the film has been improved when the substrate temperature increased from 500℃to 550℃. As the temperature of the substrate increased further, the crystalline quality of the film deteriorated. The results of Hall effect and PL measurement indicate that the Sb-doped ZnO thin films deposited at 550℃have the best optical and electrical property.(2) The experienment is to investigate the influence of different flow rates of TMSb on the ZnO thin film growth. According the results above, the substrate temperature was fixed at 550℃. The antimony-doped ZnO thin films were deposited on the same kind of substrates with the flow rates of TMSb:0.2 sccm,0.3 sccm,0.4 sccm. The samples were investigated by the same characterization methods which were mentioned above. After analyzing the test results, we found that the most proper flow rate of TMSb is 0.4 sccm because the average grain size is the biggst among the three samples and the FWHM values of the (002) diffraction peak of the XRD spectra and the NBE peak of the RT PL measurement are the smallest(The values are 0.171°and 112.3 meV respectively.). The films deposited on that condition had p-type conductivity and higher hole density and mobility.