Study of Photocarriers Lifetime Distribution in a‐Si:H via Magneto‐photoconductivity and Magneto‐Photoluminescence

Herein, the magneto-photoluminescence (MPL) of localized photocarriers and magneto-photoconductivity (MPC) of delocalized photocarriers in amorphous hydrogenated silicon (a-Si:H) films and devices, respectively, are investigated. Both responses are caused by mixing of spin sublevels in the photogenerated electron-hole (e-h) pairs that alters their recombination and dissociation rates. The spin mixing occurs by a combination of hyperfine interaction (WI) between spin 1/2 photocarriers and neighboring Si-29 and H-1 nuclei, and the Delta g mechanism which originates from a difference in the Lande g-factors of electrons and holes. The existing disorder in a-Si:H films leads to dispersive field response that is described by a unique dispersive parameter alpha < 1, from which the e-h lifetime distribution, g(tau) is obtained. The mean e-h lifetime is found to be approximate to 12 ns for the high-energy, relatively delocalized photocarriers generating the photocurrent, as compared to approximate to 200 ps for the lower energy, trapped e-h pairs which yield photoluminescence. The MPL(B) and MPC(B) responses in a-Si:H subjected to prolonged illumination that causes Staebler-Wronski type degradation, and subsequent annealing are studied. The illumination-induced photocarrier localization that enhances the HFI component is found, which dramatically decreases upon annealing; this method can assess optoelectronic device degradation.