As we know, upon illumination, electron-hole pairs generate in the semiconductor and separate due to built-in-potential at the junction. Now, my question is if the light (635 nm) illuminates on a p-type Si, how the generated e-h pairs will separate (as there is no built-in-potential in the bulk-Si)? A simple schematic of the question is illustrated in the attached figure.
Dear Abu,
the separation of electron-hole pairs requires a potential gradient. This gradient is equivalent to an electric field. If the electron hole pairs are generated within this field, a separation takes place. A constant potential or zero field doesn't effect a separation.
Electric fields can be caused by different ways:
p-n-junctions
Metal-semiconductor contacts
Gradients in doping or chemical composition
A homogenious p-type material is without effect.
With Regards
R. Mitdank
Dear Rudiger,
Thank you so much for explaining the concept clearly.
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