NASA Space Technology

Direct Detector Technology Development

LONG-TERM PROGRAM GOALS AND OBJECTIVES

The Direct Detector element, within the Sensors & Instruments element of the OACT Spacecraft & Remote Sensing/Space & Planetary technology development activity, is developing advanced devices and systems to meet a range of future mission needs. The program strives to produce mission-enhancing or mission-enabling advanced detectors in the major discipline areas of earth science, astrophysics, planetary, and space physics. Essentially, the program aims to successfully develop and thoroughly characterize detector systems which achieve optimum performance under the environmental conditions dictated by each specific space application. In many cases, this means achieving background-limited performance in a multi-element array, operating at the temperatures and integration times defined by the mission design. The program presently concentrates on advanced infrared detection techniques, and has as a goal the expansion into other parts of the electromagnetic spectrum, including advanced high-energy detectors. The program aims to involve the OSS and MTPE user communities in the definition and conduct of programs, and to accomplish effective handoffs of advanced detector technologies to the users and to the relevant project offices.

OBJECTIVES

In striving to meet these long-term goals, the program will work to achieve these specific objectives:

• Development and characterization of a 256 x 256 array of Si:As impurity band conduction (IBC) detectors for SIRTF and other applications.
• Development of advanced thermal IR detectors which operate with high sensitivity at elevated (approximately 60 kelvin) temperatures, for use in missions such as the Earth Observing System. This element includes:
  • Large silicon-based [e.g., stacked heterojunction internal photoemission (HIP)] IR detector arrays with tailorable 8 - 17 microns response.
  • Long-wavelength multi-quantum well (AlGaAs/GaAs) detector technologies.
  • Long-wave strained-layer superlattice devices (InAsSb/InSb or GaInSb/InAs)
• Development of 2-d arrays of Ge:x IBC detectors for SIRTF, SMIM, and other missions
• Development and demonstration of an advanced electron-tunneling Golay cell detector, for solar physics and terrestrial/planetary imaging applications.
• Development of advanced low-temperature readout technologies in Si, GaAs, and other materials, to support astrophysics and earth science applications.

Direct Detectors Example Roadmap (GIF format)

Direct Detecotrs Level 1 Milestones (GIF format)

Direct Detectors Ð FY '94 1st & 2nd Quarter Report -- Executive Summary

Highlights of Past Two Quarters

• SiGe/SiHIP detectors with graded boron doping profiles have been successfully fabricated and are being characterized. The graded profile introduces a built-in electric field, directing photo-excited holes toward the heterojunction. This promises to dramatically improve the photoresponse. (JPL)
• The first QWIP array (with random reflectors), built to AIRS specifications, has been delivered to the JPL characterization team. Pre-delivery data from BTL indicate that these devices have a D* of 5E10 cm Hz^0.5/W at 55 K, in the wavelength range 14.4 - 15.4 um. This is only a factor of two below the ultimate AIRS goal. (JPL)
• Fabrication and assembly of Version 1 of the 3 x 3 infrared tunneling sensor array have been completed. Preliminary testing has been completed. Data from these tests have been analyzed, and modifications to improve performance have been incorporated into the next fabrication run. (JPL)
• At JPL, GaAs junction field effect transistors (JFETs) have been successfully fabricated. Their performance at room temperature was found to be very good. Tests at liquid helium temperatures have been conducted. At 4 K, the noise was measured to be about 1 uV/rt Hz, comparable to levels achieved by silicon MOS transistors. (JPL)
• Fabrication of a second lot of the CRC-696 low-temperature (1.5 - 4 K) readouts was completed at Hughes Technology Center. Cryogenic test data from the University of Arizona and Ames showed excellent noise (20-30 e- read noise) and stability at 4 K from a multiplexing, 32-channel readout. This essentially solves a major technology concern for SIRTF. (ARC)
• Rockwell International and Cornell University demonstrated excellent performance from the latest generation of 128 x 128-element antimony-doped silicon (Si:Sb) hybrid arrays. The growth process appears to be well in hand and repeatable, and key performance parameters (e.g., cutoff wavelength, quantum efficiency, dark current) appear to meet or closely approach SIRTF goals. (ARC)
• A lot of custom readouts for the solid-state photomultiplier (SSPM) devices was fabricated for Rockwell by Orbit Semiconductor. This mask set and design was produced under an earlier Air Force contract; subsequent analysis showed that it would be very useful for astronomy/array SSPM concepts. (ARC)

Planned for Next Quarter

• Fabricate SiGe/Si detectors which include graded Ge composition within SiGa layer. (JPL)
• Produce QWIPs which include high-pass quantum filters (and random reflectors). (JPL)
• Grow and process next-generation Ge:Ga BIB detectors at Rockwell. (JPL)
• Complete fabrication/start characterization of 2nd lot of low-T Hughes FETs. (ARC)
• Start characterization of room-temperature and cryogenic performance of new Rockwell SSPM readout chips. (ARC)

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