a-Si:H photodiodes in vision applications
(English)Manuscript (preprint) (Other academic)
Advanced CMOS machine vision chips with in-pixel processing capability suffer from trade-offs in CMOS diode area vs processing circuitry. The benefit to use hydrogenated amorphous silicon (a-Si:H) diodes post-processed on the CMOS chip is both area gain and in some spectral regions increased sensitivity. Diode characteristics such as short transient response and image lag, related to machine vision application requirements are treated. Measured transient response to illumination pulses resulted in rise and fall times of shortest 2-3 S and around 7 μS respectively. The same diodes did also give longer rise times of around 30 μS, and the possible causes of the instability are discussed. Image lag was measured as an increased dark current following illumination turn-off, and was found to be small, below 50% of the very low dark current, bias-dependent and not correlated to illumination intensity. The possible influence on imager performance is discussed.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-87088OAI: oai:DiVA.org:liu-87088DiVA: diva2:584952