Determination of the optical constants of μc-Si1-xGex: H films based on the transmission spectra

作者：Huang Zhen Hua^*; Zhang Jian Jun; Ni Jian; Li Tian Wei; Cao Yu; Wang Hao; Zhao Ying

来源：Journal of Optoelectronics - Laser, 2014, 25(1): 107-112.

• Absorption co-efficient
• Advanced semiconductor analysis (ASA)
• Cauchy dispersion formula
• Hydrogenated microcrystalline silicon
• Plasma enhanced chemical vapor depositions (PE CVD)
• Swanepeol method
• Transmission spectrums
• Unconstrained minimization

In this paper, we study the optical constants of hydrogenated microcrystalline silicon germanium alloy (μc-Si1-xGex:H) fabricated by plasma enhanced chemical vapor deposition (PECVD). First we propose a Matlab method to abstract optical constants from the transmission spectra, which is based on multi-layer model and the Cauchy dispersion formula. Compared with traditional fringe pattern methods, such as Swanepeol method, pointwise unconstrained minimization approach (PUMA), the Matlab method determines the refractive index not from the amplitude of the interference fringe but from the position of the interference fringe, so it can avoid the negative influence owing to the deviation of the amplitude and can offer more precise optical constants, and it can enhance the fitting precision by one order of magnitude. The results show that the absorption coefficients and the refractive indices of μc-Si1-xGex:H are higher than those of μc-Si:H in the whole spectrum, and increase as the Ge content increases. The further results calculated by advanced semiconductor analysis (ASA) demonstrate that compared with μc-Si:H, μc-Si1-xGex:H PIN solar cells with the same thickness present higher quantum efficiency (QE) response from 400 nm when the absorber is thin, and can also achieve higher QE response in the near-infrared region when the absorber is thick. On the other hand, to realize the same current density, μc-Si1-xGex:H can reduce the thickness effectively, so it can reduce the fabricating cost of thin film solar cells apparently.

• 出版日期2014
• 单位南开大学