Structural and optoelectronic properties of a-Si:H: A new analysis based on spectroscopic ellipsometry

Hydrogenated amorphous silicon (a-Si:H) thin film has important applications in optoelectronic devices. In this work, a new analytical method of spectroscopic ellipsometry has been proposed, which can be used to calculate the density of electronic states and the optoelectronic parameters in a-Si:H. Meanwhile, the material structures, the optoelectronic properties and the relationship between them have been analyzed. Results show that the variation in electronic structure is directly related to the thin film structure. The increase of disorder in amorphous network has a strong impact on the DOS in band tails, especially in the valence band tail. The main source of variation in the peak position of dielectric function and the optical gap is the content of bonded hydrogen in the thin film. Likewise, the decrease in the amplitude of dielectric function is due primarily to the reduction in effective valence electrons induced by density deficit. Moreover, the optical absorption exhibits a contrary trend in the energy region below and above ∼1.7 eV. This is because the samples with higher deposition temperature have larger DOS in band tails and lower optical gap.