Self-Quenching Single-Photon Detector
- Wednesday, 01 October 2008
The detector has applications in nuclear physics instruments, spectroscopy, night-vision devices, and biological instrumentation.
The self-quenching single-photon detector exhibits unique avalanching behaviors. It can automatically quench each of the Geiger mode avalanche events occurring inside the detector, can maintain the capability over a broad bias range, and can output explicit pulses with virtually constant and high value gain.
A partially depleted quenching structure, which is similar to the structure of a reach-through avalanche photodiode but with significantly higher doping concentration, is the key structure of the detector. The undepleted portion of the quenching structure encloses the electric field and makes it possible for breakdown to occur in the multiplication region at a low voltage. Then, because the undepleted portion of the quenching structure forms a potential well that retards the movement of the multiplied holes, quenching can result from significant field reduction caused by holes piling up at the potential well.
A properly scaled pillar structure that contains the cathode, the multiplication region, and the quenching structure will further ensure realization of the self-quenching functionality as well as other advantages. The pillar structure’s nanoscale diameter is beneficial to other applications. A discrete, single-photon detector with a very high photon-counting rate, high quantum efficiency, and low dark count rate, as well as a photon imaging array with high spatial resolution and very high dynamic range, can be realized. A floating cathode may be incorporated on the shoulder area to help photoelectron collection.
Novel detection capabilities this innovation will enable include more convenience in single-photon detection in comparison with traditional Geiger mode avalanche photodiodes that require an external quenching circuit and a photomultiplier that is bulky and requires high voltage. With this design, single-photon detection ranging from UV (ultraviolet) to FIR (far infrared)will be enabled in the light of the structure with regard to various semiconductor materials, including silicon, germanium, silicon-germanium, SiC, III-V compounds (e.g., InGaAs/InP heterostructure, GaN and GaN/AlN), II-V compounds (e.g., HgCdTe), etc. This detector may enable the highest achievable photon counting rate up to several gigahertz due to the removal of external, parasitic capacitance, extremely small junction capacitance, and largely eliminated after-pulsing effects originating from the infinitesimally small volume of the multiplication region.
Single-photon countable, high spatial resolution, and high dynamic range imaging at the wavelengths of UV, visible, and NIR (near infrared) can be realized by monolithic silicon arrays composed of self-quenching single-photon detector pixels and on-chip readouts. Also, single-photon-countable and high dynamic range imaging at IR and FIR wavelengths will become realistic with hybrid arrays composed of a compound self-quenching single-photon detector focal plane array and a CMOS readout. A special advantage of the hybrid composition is that digital counters can be employed to read the pulse output from each pixel and result in direct digital output.
This work was done by Xinyu Zheng, Thomas Cunningham, and Bedabrata Pain of Caltech for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
Refer to NPO-43672, volume and number of this NASA Tech Briefs issue, and the page number.