Investigation of the spatial distribution of dangling bonds in light-soaked hydrogenated amorphous silicon

Article

关键词: A-SI-H;    CONDUCTIVITY CHANGES;    METASTABLE DEFECTS;    FILMS;    DEGRADATION;    SATURATION;    SURFACE;    DENSITY;   

DOI  :  10.1103/PhysRevB.53.7267

来源: SCIE

【 摘 要 】

We report on a detailed investigation of the spatial distribution of dangling bonds (DB's) in light-soaked hydrogenated amorphous silicon (a-Si:H) films. The results for light soaking at different light intensities (3 W/cm(2) and 300 mW/cm(2)) show that the inverse power-law DB distribution, N-v(x) = C(v)x(-a), holds regardless of the light soaking intensity. Here, N-v(x) is the volume density of DB's at depth x measured from the surface, and C-v and alpha(approximate to 0.6) are constants. The nonuniform spatial distribution of DB's in light-soaked a-Si:H is thought to originate from a nonuniform distribution of photocarriers during light soaking rather than from an inhomogeneity of the material. The same annealing behavior of light-induced DB's was observed regardless of the thickness of the sample and regardless of whether the sample was light soaked from one side or from both sides. This result, together with the observation of identical spin characteristics, indicates that the light-induced DB's at various depths of a given a-Si:H sample are identical in nature. The surface DB density is found to be much less sensitive to light soaking than the bulk DB density and can be assumed unchanged if the light-soaking intensity is not much higher than 300 mW/cm(2) and the light-soaking time is shorter than similar to 10 h. We show that the conventional method of estimating the surface DB density is no longer appropriate for light-soaked a-Si:H, due to the highly nonuniform distribution of DB's in the material. The nonuniform distribution of DB's can lead to significant disagreements between different techniques in quantifying the Staebler-Wronski effect and should therefore be taken into account in studies of the SW effect.

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