Origin of lateral photovoltage in hydrogenated amorphous silicon and silicon germanium thin films

Lateral photovoltage measurements in hydrogenated amorphous silicon and silicon-oxygen thin films

“…1(a) and (b), respectively. Owing to fine laser focusing and thus more intense illumination, we have successfully measured the LPV down to room temperature [1,2]. Measured LPV for a-SiO:H sample is larger at each temperature than in a-Si:H sample.…”

“…If the diffusion lengths of minority and majority carriers are very different much in the case of hydrogenated amorphous silicon (a-Si:H) and its related alloys, individual charge profiles are created and high LPV is observed. First LPV measurements in intrinsic a-Si:H was reported in [1], later in hydrogenated amorphous germanium by Srivastava et al [2], in a-Si:H and lc-Si p-i-n devices [3][4][5][6] and other device structures [7,8]. Diffusion lengths deduced from other experiments help in elucidating observed position dependence of LPV [1,2].…”

“…However, an observed variation in LPV cannot easily be related to variation in diffusion length or other material parameters. For example, LPV is found to increase with light induced degradation, where related diffusion length decreases [2,11]. Srivastava et al [2] observed an increase in LPV for their a-Si:H and a-SiGe:H films upon light induced degradation and explained their results by increase of potential fluctuations with light soaking.…”

“…For example, LPV is found to increase with light induced degradation, where related diffusion length decreases [2,11]. Srivastava et al [2] observed an increase in LPV for their a-Si:H and a-SiGe:H films upon light induced degradation and explained their results by increase of potential fluctuations with light soaking. These observations and some others that we shall outline with in this context help the current interpretation of LPV difficult to utilize for material characterization purposes to determine the ratio of carrier diffusion lengths (L n /L p ).…”

“…First LPV measurements in intrinsic a-Si:H was reported in [1], later in hydrogenated amorphous germanium by Srivastava et al [2], in a-Si:H and lc-Si p-i-n devices [3][4][5][6] and other device structures [7,8]. Diffusion lengths deduced from other experiments help in elucidating observed position dependence of LPV [1,2]. Steady State Photocarrier Grating technique (SSPG) is frequently employed to obtain diffusion length in a-Si:H [9,10].…”