SWIR and NIR MCT arrays grown by MOVPE for astronomy applications

SELEX Galileo in collaboration with the Astronomy Technology Centre (ATC) undertook an activity to develop near infrared (NIR) and short wave (SWIR) sensor arrays as a precursor to a large format array in future phases of work. In this study, SELEX grew wafers of mercury cadmium telluride (MCT) material (cut off wavelengths ranging from 1.9μm to 2.7μm) using metal organic vapour phase epitaxy (MOVPE) on GaAs substrates. With substrate sizes up to 150mm available, this technology is ideal for very large arrays. Mesa structure arrays were processed and hybridised to multiplexers with a floating gate input. MOVPE requires the growth of buffer layers which would absorb the shortest wavelengths. Results will be presented showing how the cut-on wavelength can be controlled by thinning these buffer layers and the subsequent achievement of a response to radiation shorter than 0.8 μm. Data will be presented showing sub 0.1 e/s/pix dark current at 80K, quantum efficiencies of 75% in H-band, and less than 3 minutes persistence after spot illumination into "double saturation".