Novel, Deep-UV APDs for Atomic Clocks and Space Observation

The target of this project is to develop a compact and efficient avalanche photodiode (APD) based on Al-rich AlGaN to replace currently used photomultiplier tubes in atomic clocks. The advance over existing approaches is the implementation of single crystal AlN as substrates, which practically eliminates leakage induced by threading dislocations as seen in AlGaN films grown on traditionally employed foreign substrates, such as sapphire and SiC. This enables unprecedented high gain and low noise for the UV detectors. We aim to demonstrate sensitivity over the whole deep-UV range (120 – 200 nm) while being solar and visible blind. We will provide single APDs as well as detector arrays with varying pixel resolution and pixel size. The devices will exhibit very high efficiency (> 40%) and dynamic range with sub-100 V operation. The feasibility of Geiger mode operation and photon counting will also be studied. In addition, we aim to demonstrate high linear gain and avalanche operation by relying on hign probability of electron and low probability of hole ionization for Al molar fractions exceeding 80%. When implemented into Hg-based atomic clocks, as developed for the deep space atomic clocks program, the novel APDs can lead to a significant improvement of the stability and lifetime, while at the same time reduce the volume and constraints of the accompanying electronic circuitry.

We will develop solar blind avalanche photodiodes with sensitivity in the deep-UV to replace currently-used photomultiplier tubes (PMTs) in atomic clocks being developed for the deep space program. These new detectors will be smaller, more stable, lighter, and have longer lifetime than PMTs. The novel detector will also be arranged in large 2D arrays, which will enable application for space observation such as proposed in LUVOIR, for plume detection, and for bio-chem detection applications.

The novel detector will find application in the military, research, and commercial sector for example in bio-chem detections system, for spectroscopy applications, non-line-of-sight communication, solar blind fire detection, and nuclear detection.

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