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Growth and Characterization of AlGaN Based Materials Used for Solar-blind UV Detectors of P-i-n Structure

Author: KangWei
Tutor: ChenChangQing
School: Huazhong University of Science and Technology
Course: Optical Engineering
Keywords: Metal-organic chemical vapor deposition Ultraviolet Photodetector AlGaN Window layer
CLC: TN23
Type: Master's thesis
Year: 2012
Downloads: 28
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Abstract


Recently, ultraviolet detection has been widely used in missile controlling, forecasting,biochemistry etc. AlGaN material has direct energy band, which can be adjusted from200nm to365nm by changing the Al content, and AlGaN material has good chemical properties,which makes it as a promising material for ultraviolet detector. Due to the little leakagecurrent, fast response speed and high quautum efficiency of AlGaN based solar-blind UVdetector of p-i-n structure, it has received a large number of attentions at home and abroad.However, because of leak of approptiate substrate for AlGaN epitaxy, the quality of AlGaNis still a bottleneck for the development of ultraviolet detector with excellent performance.The growth and doping of AlGaN materials with high Al content are the foundation ofAlGaN based ultraviolet detector. In this dissertation, n-AlGaN epilayers with high Alcontent （0.40.65） and AlGaN based materials used for solar-blind UV detectors of p-i-nstructure were successfully achieved by metal-organic chemical vapor deposition, which laidfoundations for the preparation of AlGaN based materials used for solar-blind UV detectors.In my work, new results are as follows:（1） The research of n doping in Al0.4Ga0.6N revealed that the electron concentration ofn-Al0.4Ga0.6N was reducing with the increasing SiH4flux. This could be attributed to thatexcess SiH4flux could induce a lot of acceptor-like defects, which can self-compensate withelectrons in n-Al0.4Ga0.6N. Due to dislocation scatter or ion scatter had a decisive influenceon mobility at different stages; the mobility of n-type film would first increase and thendecrease when SiH4flux was increased.（2） The phenomena of Al content saturation suggested that the impact of differentactivity between Al and Ga atom on AlGaN growth: the Al compositions in AlGaN epilayerswere not increased with the TMA flux. Combined with the phenomena of Al contentsaturation, the high Al content （0.40.65） n-AlGaN epilayers were successfully achieved bydecreasing the TEG flux. In addtion, the electron concentration of n-Al0.65Ga0.35N epilayerswas0.9×1018cm-3and the mobility was22.8cm2/Vs. （3） Compared with the growth of single n-Al0.4Ga0.6N layer, the research of the effect ofdifferent AlGaN window Layer on n-doped Al0.4Ga0.6N epilayers showed that the insertionof AlGaN WL could induce dislocation densities, compressive strain in n-Al0.4Ga0.6Nepilayers, which was the main reason of deterioration of crystalline quality of n-Al0.4Ga0.6N.However, the surface morphology of n-Al0.4Ga0.6N becomed bad with SiH4flux increased.When the Al content of WL was less than0.4, the increase of SiH4flux was the reason ofdecrease of conductance of n-Al0.4Ga0.6N, while the reason of decreasing conductance of n-Al0.4Ga0.6N was the insertion of AlGaN WL when the Al content of WL was more than0.4.（4） After optimization of p-doping in GaN, AlGaN based materials used for solar-blindUV detectors of p-i-n structure were successfully obtained by metal-organic chemical vapordeposition. The cut off wavelength of materials of UV detectors is267nm and thetransimssion at400nm is80%. It makes significant foundation for AlGaN based materialsused for solar-blind UV detectors of p-i-n structure.

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