Analyses of Responsivity and Quantum Efficiency of p-Si/i-β-FeSi2/n-Si Photodiodes

In this study the responsivity and quantum efficiency of p-Si/i-beta-FeSi2/n-Si double-heterostructure photodiodes and p-Si/i-Si/n-Si photodiodes are investigated by self-developed analytical methods. The dark current densities of both beta-FeSi2 and Si p-i-n photodiodes under the reverse bias condition are calculated by solving the diffusion current densities of minority carriers. The photocurrent densities of both p-i-n photodiodes under illumination with reverse bias are mainly calculated by solving the drift current densities in the depletion regions. When the beta-FeSi2 p-i-n photodiode incident wavelength, lambda, is less than 0.6 mu m, the magnitudes of responsivity and quantum efficiency are almost zero for different intrinsic thicknesses. The maximum responsivity, R = 0.65 A/W, and quantum efficiency, eta = 65%, are both at lambda = 1.2 mu m and the intrinsic beta-FeSi2 layer thickness is 100 mu m. The calculated responsivity of the Si p-i-n photodiode is consistent with the reported studies. Therefore, the analysis methods and results are valid in this work. These results indicate the high applicability of beta-FeSi2 to near-infrared photodiodes integrated with Si. Therefore, the p-Si/i-beta-FeSi2/n-Si photodiode is a new high-efficiency light sensor device applicable to optical fiber communications.