Resonant Cavity Enhanced Photodetector for Quantum Information Science Systems
This proposal addresses a need for advancements in solid state detector technologies for use in quantum information science systems—photodetector systems that simultaneously exhibit high speed (i.e., frequency bandwidth of 5 GHz) and extreme quantum efficiency (QE more than 99%) at or near traditional telecommunications wavelengths (~1.55-1.60 μm). Conventional p-i-n photodiode detectors can readily be designed to meet the frequency bandwidth target at the cost of low QE, or to approach the QE target at the cost of low bandwidth, but the simultaneous achievement of both characteristics is beyond their capability. For example, high quantum efficiency can be achieved simply by incorporating an absorbing region that is thick relative to the absorption length for incident photons. However, the long minority carrier transit time associated with a thick active region inherently limits the frequency bandwidth of such a device. Conversely, minority carrier transit time can be decreased, and frequency bandwidth can be increased by thinning the active light absorbing region, but in a conventional detector, the associated decrease in absorption probability limits QE. Amethyst Research is attempting to overcome this limitation of conventional detectors through the application of its novel Resonant Cavity Enhanced Photodetector (RCE-PD) technology. A resonant cavity enhanced photodetector includes a thin optical absorption layer located in an optical cavity between two distributed Bragg reflectors. The thin optical absorption layer allows for a short minority carrier transit time and thus high frequency bandwidth. At the same time, the resonant optical cavity created by the distributed Bragg reflectors causes light to recirculate inside the cavity, thereby enhancing the probability of absorption and resulting in high quantum efficiency. Thus, unlike a conventional p-i-n detector, Amethyst's RCE-PD technology can support the high speed as well as high QE requirements of this program. In Phase I, Amethyst and team have applied our knowledge and experience to design, grow, fabricate, and characterize a GaSb-based RCE-PD device adaptable to DOE's quantum information science needs. We have designed structures with exceptional quantum efficiency (i.e., > 99%) and analyzed their potential for high bandwidth. Experimentally, we have grown a Phase I RCE-PD structure by molecular beam epitaxy, measured the reflectance and transmittance of this structure, and fabricated and tested detectors of various sizes. The devices seem sound. The test results include spectral response, QE, and dark current as a function of temperature. The QE of this first set is not above 80%, but there are opportunities for improvement. The immediate motivation for this research is to develop quantum sensors and controls to enable emerging scientific applications. We also note that a tremendous commercialization opportunity exists because of the wavelength compatibility between this new technology and the enormous volume of already in-place conventional telecommunications infrastructure. Finally, the RCE-PD’s detection wavelength can be tuned across a broad infrared range (from 1.5-12 microns). Because of this flexibility, the resonant cavity approach in general offers additional engineering freedom as it can readily be adapted to serve a wide set of applications including optical communications, spectroscopic trace gas sensing, and real-time chemical signature monitoring.
- Research Organization:
- Amethyst Research Inc
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0021690
- OSTI ID:
- 1967882
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- Phase I Research Final Report
- Country of Publication:
- United States
- Language:
- English
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