Progress at Leonardo UK in APD array technology development for high-speed 2D linear mode photon-counting applications

Abstract

Leonardo UK high performance short waveband infrared Avalanche Photo Diode (APD) array technology is being developed for high-speed 2D linear mode photon counting, active imaging and other low flux or pulse receiver applications. APD arrays have been re-engineered for high speed and sensitivity, and fabricated in HgCdTe (MCT) using Metal Organic Vapour Phase Epitaxy (MOVPE) grown on low cost gallium arsenide (GaAs) substrates. MOVPE enables precise band gap engineering of the MCT heterostructure to implement designs that can suppress dark current, and achieve high APD gain and wide spectral responsivity at the required operating temperature. Such array structures incorporate a proprietary back plane to help reduce sensitivity of the array to de-bias or time constant effects that can otherwise reduce sensitivity, dynamic photo response, or introduce cross talk effects across the array. This paper reports technical progress and preliminary results. Array characteristics have been determined. Measuring attenuated laser pulses, a high-speed 2D array has been evaluated using a 500 ns gate. The sensor's pixel output values settle to discrete bands pulse to pulse. A histogram of the values over the range 0 -10 photons shows a characteristic Poissonian form indicating high-speed linear mode photon counting sensitivity. Future developments are identified.