Development of extended wavelength response InGaAs detectors for astronomical applications

We report the results of a program to mitigate defect induced (tunneling) dark current which arises from lattice mismatch between In0.82Ga0.18As 'extended wavelength' detector material and the InP substrate upon which it is grown. Our goal is to produce material suitable for ground-based broadband astronomical observation by achieving a dark current level in individual 25x25 mu m array pixels which is less than the atmospheric airglow and telescope thermal emission in the astronomical H (1.50-1.80 mu m) and Ks (2.00-2.32 mu m) bands. We have cryogenically tested multiple growths of candidate materials, packaged as both individual diodes and focal plane arrays, supplied by Sensors Unlimited, Inc. (SU). Results indicate dark current levels, in the current generation of array materials, surpassing the requirements for broadband imaging, and with the potential to be used for narrow band imaging and low-resolution spectroscopy.