宽带隙半导体（ZnO，SiC）材料的制备及其光电性能研究

【作者】 邓锐；

【导师】 汤洪高；

【作者基本信息】 中国科学技术大学 ， 凝聚态， 2008， 博士

【摘要】 在半导体材料的发展中,一般将Si,Ge称为第一代电子材料,GaAs,InP,GaP,InAs,AlAs等称为第二代电子材料,而将宽带隙高温半导体ZnO,SiC,GaN,AlN,金刚石等称为第三代半导体材料。随着科学技术的发展,对能在极端条件（如高温、高频、大功率、强辐射）下工作的电子器件的需求越来越迫切。常规半导体如Si,GaAs等已面临严峻挑战,故发展宽带隙半导体（E_g＞2.3 eV）材料已成为当务之急。在本论文中,我们主要讨论了宽带隙半导体材料ZnO、SiC的制备及其光电性能的研究。对于ZnO纳米材料,我们采用热蒸发法制备。我们发展了制备ZnO纳米柱阵列的热蒸发法。实验不需要引入催化剂,也不需要预先沉积ZnO层,用廉价的硅衬底代替昂贵的蓝宝石衬底,在常压下得到了结晶质量好的样品。我们在较低生长温度（550℃）下,获得了结晶质量好的,高度定向的ZnO纳米柱阵列,而且,我们研究了物性和讨论了生长机制。分别在550℃,600℃和650℃下。采用热蒸发法,合成了ZnO:Li纳米线,发现在600℃下合成的样品的紫外发光峰是550℃下合成的样品的十几倍,我们把这种现象归结于Li的掺杂引入了受主,受主浓度的增大让激子浓度变大。最后作出它的气敏器件。在680℃时,采用不同源不同温度的方法,合成了ZnO:Al纳米线。发现它的紫外发光峰有蓝移现象,我们把这种现象归结于著名的B-M（Burstain-Moss）效应。对于ZnO薄膜材料,我们采用了PLD（脉冲激光沉积）法制备。采用Si衬底上制备ZnO薄膜的过程中,克服Si衬底与ZnO薄膜之间高达40%的晶格失配,减少由此产生的缺陷,在400℃下沉积得到较高质量的ZnO薄膜,在此基础上,研究ZnO/p-Si薄膜光电性能。我们采用SiC做衬底,外延生长高质量的ZnO薄膜。在400℃下沉积得到较高质量的ZnO:Ag薄膜,得到较稳定的p型特性。Ag掺入ZnO时,Ag占据Zn态,形成Ag_Zn受主。并讨论了Ag在ZnO中的存在的形态。对于SiC薄膜材料,我们采用了PLD（脉冲激光沉积）法制备。在C气氛下,于800-1200℃退火处理2小时。通过XRD,红外和XPS等一系列的测试手段表明,在1200℃退火,能很好抑制SiC的氧化和C的逃逸。得到很好结晶质量的SiC和较好的化学剂量比的。更多还原

【Abstract】 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℃.更多还原