|United States Of America||Issued Patent||8,809,672||08/19/2014||2009-123|
|United States Of America||Issued Patent||8,673,680||03/18/2014||2009-123|
The invention is about an extremely efficient photodiode and solar cell using a novel nanoneedle structure to create a large internal field for electron-hole amplification and collection, and a plasmonic antenna for optical field enhancement. Both of which work together to result in an extremely high efficiency. Investigators at UCB have demonstrated one version of this detector in the format of an avalanche photodetector (APD) based upon a crystalline GaAs nanostructure in the shape of a very sharp nanoneedle (NN) and incorporating a core-shell p-n junction for light detection. The tapered NN shape, high NN aspect ratio, and small NN dimension together allow a low bias voltage to produce a high electric field sufficient for current multiplication for high sensitivity. NN APDs also have an extremely high operation speed due to the reduced capacitance comimg from the small NN dimensions. The catalyst-free, low-temperature growth mode of the GaAs NNs also enables the integration to the as-fabricated Si CMOS devices as well as other crystalline or amorphous substrates.