Development of a large scale stressed Ge:Ga detector array for SAFARI

We report on the development of a large-format stressed gallium doped germanium (Ge:Ge) array for the SAFARI instrument planned for the Japanese infrared satellite SPICA. Building on flight proven PACS heritage, the goal of our development is a 32 pixel stressed Ge:Ga module for the wavelength range between 110 and 210 μm, being the building block of a 32 × 32 pixel detector array. The unprecedented size of this array would allow the use of almost all of the 3.8 × 3.8 arcmin field of view available to SAFARI in the SPICA focal plane. Our 32 pixel prototype module features three selectable read-out architectures enabling the evaluation and optimization of the detector performance as well as a two stage multiplexer to distribute the dissipative heat load on the temperature stages provided by the satellite. Thermal modeling has shown that the heat loads are in compliance with the thermal budgets of the SPICA cryogenic system. The ultimate development goal with optimized read-out circuits is an NEP of 1 × 10-18 W/Hz1/2, which presents a factor of 8 improvement in noise performance compared to the PACS stressed Ge:Ga array.

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