An SOI Photodetector With Field-Induced Embedded Diode Showing High Responsivity and Tunable Response Spectrum by Backgate

In this paper, we demonstrate experimentally a photodetector based on silicon-on-insulator substrate. The photosensing diode is formed in the substrate induced by the backgate bias instead of doping. TCAD simulation is conducted to confirm that the field-induced junction performs similarly as the doped p-n junction in terms of photodetection. A simplified process flow with low process temperature is developed to fabricate the device, which can save implantation step and reduce the cost. The photoresponses of the device under various biases, light intensities, and wavelengths are studied systematically with both experiment and TCAD simulation. Responsivity up to 1150 A/W is achieved experimentally. In addition, the response spectrum can be modulated by the back gate bias, which is a very attractive feature for multiband photodetection application. The field-induced photodiode in the substrate modulates the threshold voltage of the MOSFET at top Si layer as efficiently as the doped junction, confirmed by TCAD simulation.