Observed Similar Behavior of a-Si: H P-I-N Photodiode and Retina Response

V. Gradišnik (Croatia)


a-Si:H, defects, photodiode, ERG, retina


Epiretinal and subretinal prosthesis implants, composed mostly of silicon CMOS neuromorphic chips have recently been proposed. In this paper, we present measurements that detail the similarities between some mammillae retinal responses, monitored by electroretinography (ERG) and those of a-Si:H p-i-n photodiode (PD) response. The PD response on simultaneous voltage and light pulses has a similar shape as retinal layers response. The characteristic shape of PD response, ascribed here to trap states, is analyzed. The optimal parameters (amplitude, duration, waveform and frequency) and threshold voltages of the a-Si:H p-i-n photodiode responses were identified. The voltage pulse influence on photodiode response can be compared with activities of bipolar cells in retinal response. Previously described PD behaviour suggests potential use of a-Si:H p-i-n PD as active pixel in retinal implant.

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