Wide Band Gap Semiconductor (zno, Sic) Material Preparation And Optical And Electrical Properties

In the development of semiconductors,Si and Ge is the first generation,GaAs,InP, GaP,InAs and AlAs is the second generation,while the third generation consists of ZnO, SiC,GaN,AlN and diamond etc.With the rapid advance of science and technology, common semiconductor such as Si and GaAs is not competitive for the applications in microelectronic and optoelectronic devices designed to operate in severe conditions(high temperature,high power,high frequency,etc).Therefore,the research and development of wide-band-gap semiconductor(Eg＞2.3 eV)is very important and urgent.In this thesis,we mainly discussed the synthesis and properties of ZnO and SiC.For ZnO nanorods by a simple thermal evaporation case,The main conclusion can be summarized as follows:High-density well-aligned ZnO nanorod array was synthesized at 550℃without catalyst,Al₂O₃ substrate and the pre-deposited ZnO film by a simple thermal evaporation in normal pressure.In addition,Furthermore,the growth mechanism and physical properties were discussed.Well-aligned ZnO:Li nanorod arrays with various Li concentrations were prepared on Silicon substrate by a simple vapor deposition at 550℃,600℃and 650℃, respectively.The gas sensing properties indicate that the structure of energy band of ZnO:Li is different from that of undoped ZnO.The strongest UV emission of ZnO:Li sample prepared at 600℃was over ten times stronger than that of the ZnO nanowire prepared at 550℃,which is considered to be due to Li doping.Well-aligned AlZnO nanorod arrays with various Al concentrations and various diameters were prepared at 680℃on Silicon substrate by a simple vapor deposition with separate sources at different temperatures.Photoluminescence(PL)spectra reveal that a strong ultraviolet emission shifts to a higher energy due to Al incorporation.This is the well-known Burstain-Moss effect.For ZnO thin film by PLDcase,The main conclusion can be summarized as follows:Highly c-axis oriented and good crystallinity ZnO on Si substrate at 400℃. Furthermore,the physical properties of the ZnO/p-Si were discussed.A better crystallinity ZnO at 6H-SiC were prepare.ZnO:Ag films have been fabricated on a n-Si(111)substrate at 400℃.Furthermore, Ag dopants prefer to occupy the substitutional Zn sites,and an Ag substitution at a Zn site behaves as a deep accetor.For SiC thin film by PLD case,The main conclusion can be summarized as follows:These films were annealed isochronally at temperatures of 800℃-1200℃for 2 h under an C ambience.The XRD,IR and XPS show that the optimized annealed temperature is 1200℃.