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 incumbent 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 screw dislocations as seen in abundance in thin films of AlGaN 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 far UV range (120 ndash; 240 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 sensitivity (gt; 40%) and dynamic range with sub-200 V operation. Furthermore, we will demonstrate operation in Geiger mode which enables single photon detection in the UV range. In addition, we aim to demonstrate high linear gains and avalanche operation by employing the improbability of hole ionization for Al molar fractions exceeding 80%. Our proposal aims to demonstrate significant improvement in AlGaN based detectors. When implemented into Hg based atomic clocks, as developed in 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 reducing volume and constraints to the accompanying electronic circuitry. Beyond application for atomic clock the far UV APDs could be used for space observation such as proposed in LUVOIR, for plume detection, or for bio-chem detection applications.