Leonardo large area avalanche photo-diode arrays

Leonardo produces a renowned Saphira 24um pitch APD sensor, widely used for wavefront sensing down to sub photon threshold levels. With the current interest in the detection of exoplanets and other faint objects at or around room temperature, Leonardo has designed and fabricated an enlarged version of the APD device. The new device features 2048 pixels x 2048 pixels on a 15 micron pitch, designed to accommodate Leonardo’s avalanche Photo-diode MCT structures. The new design incorporates Leonardo’s proven radiation hard cell library meaning the device is suitable for a future space flight programme. Whilst the new device features a smaller pitch than the original Saphira, successful APD devices have already been demonstrated on the 15um pitch Ike Pono array. Defect levels of less than 0.01% on 15 micron pitch devices have been seen, together with APD gain levels of greater than 20, using a 12 volt detector bias. Our paper describes the progress of an ESA / Leonardo contract (reference 4000130154/20/NL/AR) to design the ROIC and to fabricate and test arrays at a range of cryogenic temperatures from 70 to 100 Kelvin. The new ROIC maintains the existing flexible readout modes, including non-destructive readout, interleaved with reference rows readout between active rows, as well as a read-reset-read mode. Leonardo have also introduced new functionality including a windowing mode where sub windows per output bank can be defined, as well as multi row windowing. Flexible pixel reset operations are available with global reset, row by row reset and pixel by pixel reset options.