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采用椭圆偏振光谱法,在1.50～6.50 eV光谱内,研究了在蓝宝石衬底(0001)面上使用金属有机化学气相沉积(MOCVD)的方法制备的非掺杂纤锌矿结构GaN薄膜的光学性质。建立GaN表面层/外延层/缓冲层/衬底四层物理结构模型。与Cauchy和Sellmeier色散公式比较后选择了Tanguy Extended色散公式来分析GaN薄膜的光学性质。椭圆偏振光谱拟合结果表明,Tanguy Extended色散公式能更准确、方便地描述GaN薄膜在全波段(特别是带隙及带隙之上波段)的色散关系。提供了GaN薄膜在1.50～6.50 eV光谱范围内的寻常光(o光)和非寻常光(e光)折射率和消光系数色散关系,为定量分析GaN薄膜带边附近各向异性的光学性质提供了依据。
The optical properties of undoped wurtzite GaN films prepared by metalorganic chemical vapor deposition (MOCVD) on sapphire substrate (0001) surface were investigated by ellipsometry in the 1.50-6.50 eV spectra. . A four-layer physical structure model of GaN surface layer / epitaxial layer / buffer layer / substrate is established. After comparing with the Cauchy and Sellmeier dispersion formulas, the Tanguy Extended dispersion formula was chosen to analyze the optical properties of GaN films. The results of ellipsometry show that the Tanguy Extended dispersion formula can describe the chromatic dispersion of GaN thin films more accurately and conveniently in all wavebands (especially above the band gap and band gap). The refractive index and extinction coefficient dispersion of ordinary (o-light) and extraordinary (e-light) of GaN film in the 1.50-6.50 eV spectral range are provided for the quantitative analysis of the optical properties of the anisotropy in the vicinity of the GaN film The basis.