engleski

The a-Si:H Device Characteristics Degradation Upon the Light Induced Defects

The transient photocurrent of reverse and forward biased a‐Si:H pin devices to blue light impulses and simultaneous illumination with a blue bias beam of the same intensity have been investigated. The modified optical bias dependence of modulated photocurrent method ‐ OBMPC at low frequency is used to measure the devices responses. The device responses were analysed as a sum of decaying exponential functions using the linear least squares method. The linearization was achieved by successive numerical integration first proposed by Foss. The sum of decaying exponentials is typical response for independent relaxation processes happening in parallel. The interpretation of results leads to estimation of localized states energies in amorphous silicon i‐layer, as well as their influence on photocurrent and capacitance degradation. It is observed that the defect states of i‐layer are distributed around deeper energy levels at reverse bias than at forward bias voltages. Also, the small increase in energies of localized states is observed in region where the capacitance achieves the upper limit close to the built‐in potential. The proposed method can be used to characterize the localized states of the native and light‐induced defect states in a‐Si:H devices and their influence on device performances.

a‐Si:H devices, transient response, OBMPC, low frequency

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