Structural and electronic properties of hydrogenated polymorphous silicon films deposited at high rate
Résumé
Structural and electronic defect-related properties of hydrogenated polymorphous silicon (pm-Si:H) films deposited at high rates of up to 9 Å/s have been investigated. Raman spectroscopy reveals the usual peaks characteristic of the amorphous nature of the material, as well as intermediate peaks associated with the effect of nanocrystallites in the amorphous matrix. These results have been correlated with infrared measurements. Transport and defect-related properties deduced from a set of complementary techniques show that hydrogenated polymorphous silicon presents better properties compared to the standard amorphous silicon (a-Si:H). In particular, capacitance measurements on Schottky diodes reveal a very low density of states at the Fermi level. Based on experimental results, band gap states modeling has been achieved for pm-Si:H and a-Si:H by means of a numerical calculation software. Some parameters that are not directly measured with experiments, such as capture cross sections, could be deduced from simulations and differences between pm-Si:H and a-Si:H could be further revealed.