热壁外延碲化镉薄膜光学特性的分析及测试  

OPTICAL PROPERTIES ANALYZING AND MEASURING OF CdTe THIN FILMS GROWN BY HOT WALL EPITAXY

作　　者：陈庭金[1] 姚朝晖[1] 王履芳[1] 汤叶华[1] 夏朝凤[1] 袁海荣[1] 

机构地区：[1]云南师范大学太阳能研究所,昆明650092

出　　处：《太阳能学报》2007年第8期936-941,共6页Acta Energiae Solaris Sinica

基　　金：国家自然科学基金项目(NO.50362003);云南省自然科学基金项目(NO.200250037)

摘　　要：用热壁外延的方法,在清洁的玻璃衬底上外延生长了不同厚度的CdTe薄膜,对薄膜的本征吸收光学特性进行了全面的研究分析和测量。对玻璃衬底的样品模式:空气-CdTe薄膜-玻璃-空气系统经光照的反射、吸收和透射问题进行了严格的数学处理,给出了总反射率和透射率的表达式。用Cary5000型双光束分光光度计测试了样品薄膜的反射谱和透射谱,据测量结果经数学处理,计算得到了描述薄膜宏观光学特性的重要物理量,即薄膜的本征光学吸收系数、消光系数、折射率和联系宏观可测量与微观量之间桥梁作用的复介电函数ε=ε1-iε2。用"Tauc"作图法,得到了薄膜的光学能隙Egopt,证明了材料是直接带隙结构,得到了薄膜厚度分别为0.12、0.48、0.81μm时相应的多晶晶粒尺寸增大的样品,其光学能隙分别变窄为1.54、1.48和1.46eV,向单晶CdTe能隙值1.44eV逼近。薄膜在本征吸收的可见光区有高的吸收系数。CdTe thin films with different thicknesses are prepared on well-cleaned glass grown by Hot Wall Epitaxy, and their optical properties are comprehensively studied and measured. The reflectance, absorptance and transmittance of thin film are discussed from and illuminated specimen with Air-CdTe thin film-Gass-Air mode, and their formulation of total reflectance and transmittance are given. The reflectance spectra and transmittance spectra are measured by the Cary5000 Double Beam Spectrometer from 200 to 1200nm, and calculated absorption coefficient, extinction coefficient and reflective index as well as dielectric function（ε^-=ε1-iε2 ）are obtained in the intrinsic absorption region. A plot of （ahv）^2 versus hv is used to determine the optical energy gap Es of CdTe thin films. It is found that thd optical energy gap Es decreases with the increase of thickness, possible due to a large grain size. These results confirm that CdTe is a direct gap material with a high absorption coefficient in the intrinsic absorption region.

关 键 词：热壁外延 CDTE薄膜 光学特性 测量 

分 类 号：TK511[动力工程及工程热物理—热能工程]