Trial Manufacturing of An InGaAs 2-D Detector Array for Astronomical Observations

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InGaAs photovoltaic detectors have been developed and evaluated. Comparison of InGaAs with other detectors has been made. We have completed the evaluation of one dimensional arrays in laboratories and at a telescope, and have not proceeded to development of a two dimensional array. [Dark current and quantum efficiency] The temperature dependence of dark current of single and 16-ch array InGaAs detectors was measured from a room temperature to 200K and 95K, respectively. The dark current shows sufficient decrease at 95K, but the quantum efficiency of the detector for long wavelength radiation decreases there ; its cutoff wavelength decreases from 1.7 mum (room temperature) to 1.55 mum (95K) . [Evaluation at telescope] An 128-ch InGaAs array was on the Nagoya University 50-cm telescope with optical fibers and a grating to make a spectrometer with spectral resolution of lambda/DELTAlambdaSOOO.We obtained spectra of bright stars at 1.3 mum, which show the Pa beta absorption and telluric absorptions. [Comparison with other detectors] An electronics system which can drive two dimensional arrays has been developed ; its speed and noise characteristics are sufficient for detector arrays of astronomical use. In comparison with other arrays, we conclude that InGaAs has merits such as low dark current and high operation temperature, but that the decrease of its efficiency at 1.55 mum poses a difficulty in astronomical applications.