CCD Readout of infrared hybrid focal-plane arrays

Abstract

In this paper, we discuss different modes of coupling photovoltaic detectors to a readout silicon CCD in infrared hybrid arrays, and we analyze, for different types of application, the critical parameters and the related structures. We also give experimental results for the readout of Pb 0.80 Sn 0.20 Te detectors (sensitive in the 8-12-µm range) operated at 77 K, direct-injection coupled to a linear multiplexing silicon CCD. The measured injection efficiency (65 percent), the dispersion in detector biasing (15 to 25 mV), amplitude modulation (±15 percent), and the measured equivalent detectivity (>2.10 ¹⁰ cm/W . Hz ^1/2 ) are in good agreement with values that were calculated from the characteristics of the detectors and the multiplexing CCD. At present, the equivalent detectivity is limited by the coupling noise current in the MOSFET channel of each CCD input. An equivalent detectivity of better than 5.10 ¹⁰ is anticipated for 8-12-µm photovoltaic detectors that are operated at 60 K. We also give results for an area hybrid array of 8-12-µm photovoltaic detectors on a silicon CCD. A specific detectivity of 2.10 ¹⁰ W ^-1 . cm . Hz ^1/2 has been obtained with direct detector readout. A silicon CCD multiplexer has proved to be effective for reading out 8-12-µm infrared photovoltaic detectors (HgCdTe, PbSnTe). It should also be well suited to the readout of 3-5-µm infrared photovoltaic detectors (HgCdTe, InSb, InAsSb).