Sensitive Photodetection Based on the Surface States of p-Type Silicon

We report a new photodetector based on the surface states of p-type silicon. By combining the application of external fields with laser illumination, the current intensity on the surface of p-type silicon is 578 times larger than that only applied by external fields. Intriguingly, the change of current is closely related to the laser position, and we can detect an obvious current change even if the laser position is more than 1000 mu m away from the electrode. We attribute this to a combined effect: the lateral photovoltaic contribution induced by the surface state of p-type silicon and a sharp increase of photo-excited carriers on the surface due to the change of depletion layer caused by external electric fields. This result provides the possibility for the future use of p-type silicon in the field of photodetection. Due to its sensitivity, simpler structure, and low cost, this kind of the photodetector is expected to be a promising photodetector.