32 pixel FIRGA demonstrator-testing of a gallium arsenide photoconductor array for far infrared astronomy

摘要

A gallium arsenide photoconductive detector, which is sensitive in the far-infrared wavelength range from approximately 60 mu m to 300 mu m, offers the advantage of extending considerably the long wavelength cut-off of presently available photodetectors. FIRGA is an ESA spnsored GaAs detector development program which is approaching completion. The FIRGA study is intended to prepare the technology for large two-dimensional GaAs detector arrays for far-infrared astronomy. The primary goal of the development is the preparation of a monolighic 32 element demonstrator array module with associated crysogenic read-out electronics. Continuous progress in material research has led to the production of pure and doped n-type GaAs layers using liquid phase epitaxy (LPE). We prepared sample detectors from those materials and investigated their electrical and infrared characteristics. Finally, a multi-layer structured detector device was manufactured. The 4x8 element array configuration is defined by sawing a slit pattern into the layers with pixel size 1mm x 1mm. The device is back illuminated. The 32 pixels are connected to two cryogenic read-out electroics chips mounted close-by. Results of the initial detector performance tests are reported. We determined dark current, responsivity and response transients. Ongoing development activities will concentrate on material research, i.e. the production of n-GaAs layers of ultra-high purity and those with improved FIR characteristics using new centrifugal techniques for material growth.