Depletion mode thin film semiconductor photodetectors

Abstract

Abstract A depletion mode thin film semiconductor photodetector comprises a crystalline silicon thin film on an insulating substrate with a source region, a drain region and a thin film light sensing channel region formed therebetween. A gate oxide formed over the channel region and a gate electrode formed on the gate oxide. A p-n junction located parallel to the surface of the substrate and within the thin film functioning as a space charge separation region in the channel. The lower portion of the channel region is a p region extending to the substrate and the upper portion of the channel region is a n region extending to the gate oxide. The channel region functions as a fully depleted channel when the photodetector is operated in its OFF state providing for high dynamic range and large photocurrent operation. The depletion mode thin film semiconductor photodetector with n + source and drain regions function as an ohmic contacts to the channel n region forming a thin film transistor. The thin film transistor photodetector has high photoconductive gain at low light intensities when the n channel region is fully pinched off by an applied gate voltage to the gate electrode which is sufficiently negative as compared to the threshold voltage of the photodetector. When the drain region is replaced by a p + region functioning as an ohmic contact to the channel p region, a depletion mode gated diode is formed. When the channel region is extended to include a plurality of linearly spaced gate electrodes formed on the gate oxide region with an input diode formed adjacent to the first of such gate electrodes and an output diode formed adjacent to the last of such gate electrodes, the photodetector functions as a charge coupled device.

Inventors

• 👤 Anne Chiang
• 👤 Noble M. Johnson

Bibliographic Details