Gary C. Bailey

Recent Developments on a 128 x 128 Indium Antimonide/FET Switch Hybrid Imager For Low-Background Applications

By combining high-quality mesa photovoltaic indium antimonide detector material with a silicon x-y FET switch multiplexer, a useful infrared area detector has been developed. This device is intended for low-background applications, where high sensitivity is required. Initial characterization of the detector at 80 K showed a KTC limited read noise of less than 1,000 electrons, good dark current, responsivity uniformity, and a maximum readout rate of 10 MHz. The hybrid mating technology has sufficient precision to allow expansion to a 256 x 256 format. The dark current in the detector material is sufficiently low to allow full-frame integration, even with arrays as large as 256 x 256 elements.

A 256 By 256 Hgcdte Hybrid Focal Plane For Low-Background Earth Resources And Astronomy Applications

This paper describes a 256 by 256 HgCdTe hybrid focal plane with a 0.9 to 2.6 μm spectral range. The silicon FET switch multiplexer (mux) is based on previous hybrid work with a 128 by 128 Reticon mux. The high-density device described has a 40 μm pixel pitch vs. 60 gm for the 128 by 128 devices. A read noise of about 1,000 e-has been obtained on developmental hybrid structures, along with full well capacities of about 1 x 106 e-. Preliminary device characterization for the 256 by 256 device, along with the first low-background astronomy test results for the 128 by 128 devices, will be presented.

Visible And Infrared Linear Detector Arrays For The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument uses four separate focal plane assemblies consisting of line array detectors that are multiplexed to a common J-FET preamp using a FET switch multiplexing (MUX) technique. A 32-element silicon line array covers the spectral range from 0.41 to 0.70 pm. Three additional 64-element indium antimonide (InSb) line arrays cover the spectral range from 0.68 to 2.45 pm. The spectral sampling interval per detector element is nominally 9.8 nm, giving a total of 224 spectral channels. All focal planes operate at liquid nitrogen temperature and are housed in separate dewars. Electrical performance characteristics include a read noise of < 1000 e- in all channels, response and dark nonuniformity of 5% peak to peak, and quantum efficiency of ) 60%.

Astronomical camera using a high-performance indium antimonide linear array

For the past several years, Jet Propulsion Laboratory (JPL) personnel have worked with Cincinnati Electronics to develop high-performance infrared line arrays using photo-voltaic Indium Antimonide coupled to a Peticon MOS-switch multiplexer. The result is a high-performance integrating detector which has been demonstrated with integration times up to one hour at 46K.

Short Wavelength 128 By 128 Focal Plane Arrays For Remote Sensing Applications

Short wavelength (1-2.5 μm) 128 by 128 focal plane arrays have been fabricated and demonstrated with high pixel yields and dark current limited performance. Smaller arrays (32 by 32 and 64 by 64) have already been used successfully in the Airborne Imaging Spectrometer (AIS) instrument in the United States, Australia, and Western Europe. Ground-track swath width is enhanced by the development of 128 by 128 arrays. The long-term goal is to develop a 150 by 1000 mosaicked focal plane for use in the High Resolution Imaging Spectrometer (HIRIS) instrument, a facility instrument on the Earth Observing System (Eos). This instrument will map the earth with from 5 to 10 nm spectral resolution and 30 m spatial resolution for flux levels of 1010 to 1012 ph/cm2-s with An f/3.8 optical system. The detector material is HgCdTe grown by liquid phase epitaxy on a sapphire substrate which yields high-performance uniform detectors. The detectors are ion implanted photodiodes with ZnS passivation. They are mated to a silicon multiplexer through indium columns to fabricate the hybrid. Operational pixel yields of greater than 99 percent have been obtained. Reliability tests on 128 by 128 hybrids show that the device is mechanically durable to more than 50 thermal cycles. The detector arrays have been characterized at temperatures of 80-150 K. Mean RoA values of 4 x 106 ohms-cm2 and leakage currents below 5 x 10-13 A have been measured at 150 K. The peak quantum efficiency at 2.4 μm is 80 percent. These results indicate that the detectors have sufficient performance for dark current limited operation at low scene albedos. The multiplexer is an EG&G Reticon FET switch imager with two output amplifiers. It is a standard visible imager that has been modified for indium column growth and detector substrate bias control. The internal circuitry has not been changed. The charge is integrated in the detector capacitance under reverse bias and then transferred through common video lines into odd and even bucket brigades and clocked out through the output amplifiers. The read noise of the multiplexer is 950 electrons, and the maximum readout rate is 10 MHz. The maximum charge storage capacity is 5 x 106 electrons.

Operation Of Integrating Indium Antimonide Linear Arrays At 65 K And Below

The combination of a FET switch non-CCD readout architecture with high-quality mesa photovoltaic indium antimonide detector material has led to high-performance integrating linear imagers in the 1- to 5-pm region. These devices operate in the temperature regime below 100 K and provide very good dark current and responsivity uniformity (±2%). Test data will show performance at 65 K for a 512-element array and 46 K for a 128-element array. Useful integration times of 3600 seconds at 46 K and >12 seconds at 65 K have been achieved. kTC read noise levels of less than 1200 electrons have been measured for both devices.

Near-Infrared Linear Array Spectrometer For Space Applications

A 128-element InSb linear detector array read out with a field effect transistor (FET) multiplexing scheme has been developed at the Jet Propulsion Laboratory: State-of-the-art NEP, uniform response, on-detector charge integration, and very low focal plane heat load compared to that of discreet detector arrays allows this type of array to open new possi-bilities for spaceborne near-infrared imaging spectrometers. Large number of cooled detector elements are feasible with the new technology, making it practical to design sensitive spectrometers even for spinning spacecraft where simultaneous wavelength coverage is necessary to avoid confusion of spatial with spectral variations.