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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Quantum Well Infrared Photodetector (QWIP) Focal Plane Arrays

Intrinsic infrared detectors in the long-wavelength range (6 - 20 ??are based on interband transition which promotes an electron across the band gap (E(sub g)) from the valence band to the conduction band.

IR QWIP Focal Plane Arrays Quantum Wells Infrared↗
NASA NTRS2007

InGaAsP Avalanche Photodetectors for Non-Gated 1.06 micrometer Photon-Counting Receivers

The efficient detection of single photons at 1.06 micron is of considerable interest for lidar/ladar systems designed for remote sensing an d ranging as well as for free-space optical transmission in photon-st arved applications. However, silicon-based single photon avalanche diodes (SPADs) used at shorter wavelengths have very low single photon d etection efficiency (approximately 1 - 2%) at 1.06 micron, and InP/In GaAs SPADs designed for telecommunications wavelengths near 1.5 micro n exhibit high dark count rates that generally inhibit non-gated (free-running) operation. To bridge this "single photon detection gap" for wavelengths just beyond 1 micron, we have developed high performance , large area (80 - 200 micron diameter) InP-based InGaAsP quaternary absorber SPADs optimized for operation at 1.06 micron and based on a highly reliable planar geometry avalanche photodiode structure. We wil l show that dark count rates are sufficiently low to allow for non-ga ted operation while achieving detection efficiencies far surpassing t hose found for Si SPADs. At a detection efficiency of 10%, 80 micron diameter devices exhibit dark count rates below 1000 Hz and count rate s of at least 3 MHz when operated at -40 C. Significantly higher dete ction efficiencies (30 - 50%) are achievable with acceptable tradeoff s in dark count rate. In this paper, we will also discuss performance modeling for these devices and compare their behavior with longer wav elength InP-based InGaAs ternary absorber SPADs fabricated on a relat ed device design platform.

Itzler, Mark A.↗
NASA NTRS2005

Active pixel sensor pixel having a photodetector whose output is coupled to an output transistor gate

An imaging device formed as a monolithic complementary metal oxide semiconductor integrated circuit in an industry standard complementary metal oxide semiconductor process, the integrated circuit including a focal plane array of pixel cells, each one of the cells including a photogate overlying the substrate for accumulating photo-generated charge in an underlying portion of the substrate and a charge coupled device section formed on the substrate adjacent the photogate having a sensing node and at least one charge coupled device stage for transferring charge from the underlying portion of the substrate to the sensing node. There is also a readout circuit, part of which can be disposed at the bottom of each column of cells and be common to all the cells in the column. A Simple Floating Gate (SFG) pixel structure could also be employed in the imager to provide a non-destructive readout and smaller pixel sizes.

Fossum, Eric R.↗
NASA NTRS1986

CCD imager with photodetector bias introduced via the CCD register

An infrared charge-coupled-device (IR-CCD) imager uses an array of Schottky-barrier diodes (SBD's) as photosensing elements and uses a charge-coupled-device (CCD) for arranging charge samples supplied in parallel from the array of SBD's into a succession of serially supplied output signal samples. Its sensitivity to infrared (IR) is improved by placing bias charges on the Schottky barrier diodes. Bias charges are transported to the Schottky barrier diodes by a CCD also used for charge sample read-out.

Kosonocky, Walter F.↗
NASA NTRS2012

Quantum-Well Infrared Photodetector (QWIP) Focal Plane Assembly

A paper describes the Thermal Infrared Sensor (TIRS), a QWIP-based instrument intended to supplement the Operational Land Imager (OLI) for the Landsat Data Continuity Mission (LDCM). The TIRS instrument is a far-infrared imager operating in the pushbroom mode with two IR channels: 10.8 and 12 microns. The focal plane will contain three 640x512 QWIP arrays mounted on a silicon substrate. The silicon substrate is a custom-fabricated carrier board with a single layer of aluminum interconnects. The general fabrication process starts with a 4-in. (approx.10-cm) diameter silicon wafer. The wafer is oxidized, a single substrate contact is etched, and aluminum is deposited, patterned, and alloyed. This technology development is aimed at incorporating three large-format infrared detecting arrays based on GaAs QWIP technology onto a common focal plane with precision alignment of all three arrays. This focal plane must survive the rigors of flight qualification and operate at a temperature of 43 K (-230 C) for five years while orbiting the Earth. The challenges presented include ensuring thermal compatibility among all the components, designing and building a compact, somewhat modular system and ensuring alignment to very tight levels. The multi-array focal plane integrated onto a single silicon substrate is a new application of both QWIP array development and silicon wafer scale integration. The Invar-based assembly has been tested to ensure thermal reliability.

Jhabvala, Murzy↗
NASA NTRS2014

Development of Cryogenic Filter Wheels for the HERSCHEL Photodetector Array Camera & Spectrometer (PACS)

This paper describes the two PACS Filter Wheels that are direct-drive rotational mechanisms operated at a temperature below 5K inside the PACS focal plane unit of the Herschel Satellite. The purpose of the mechanisms is to switch between filters. The rotation axis is pivoted to the support structure via a slightly preloaded pair of ball bearings and driven by a Cryotorquer. Position sensing is realized by a pair of Hall effect sensors. Powerless positioning at the filter positions is achieved by a magnetic ratchet system. The key technologies are the Cryotorquer design and the magnetic ratchet design in the low temperature range. Furthermore, we will report on lessons learned during the development and qualification of the mechanism and the paint.

Koerner, Christian↗
NASA NTRS2014

Advanced Photodetectors for Space Lidar

The detector in a space lidar plays a key role in the instrument characteristics and performance, especially in direct detection lidar. The sensitivity of the detector is usually the limiting factor when determining the laser power and the receiver aperture size, which in turn determines the instrument complexity and cost. The availability of a suitable detector is often a deciding factor in the choice of lidar wavelengths. A direct detection lidar can achieve the highest receiver performance, or the quantum limit, when its detector can detect signals at the single photon

PMT↗
NASA NTRS2015

Superlattice Infrared Photodetector Research at the Jet Propulsion Laboratory

III-V semiconductors offer a highly effective platform for the development of sophisticated heterostructure-based MWIR and LWIR detectors, as exemplified by the high-performance double heterostructure (DH) nBn, XBn, and type- II superlattice infrared detectors. A key enabling design element is the unipolar barrier, which is used to implement the complementary barrier infra-red detector (CBIRD) design for increasing the collection efficiency of photo-generated carriers, and reducing dark current generation without impeding photocurrent flow. Heterostructure superlattice detectors that make effective use of unipolar barriers have demonstrated strong reduction of generation-recombination (G-R) dark current due to Shockley-Read-Hall (SRH) processes. In the last several years we solely focused on the development of antimonide based IR detectors. Recently, we demonstrated RoA values over 14,000 Ohm sq cm for a 9.9 micron cutoff device by incorporating electron-blocking and hole-blocking unipolar barriers. This device has shown 300K BLIP operation with f/2 optics at 87 K with blackbody D* of 1.1x10(exp 11) cm Hz1/2/W.

focal planes↗
NASA NTRS2018

Fast, Large Area, Wide Band GAP UV Photodetector for Cherenkov Light Detection

A solid-state radiation detector includes a pattern of conductive metal on a zinc oxide substrate. The pattern provides an arrangement of interdigitated electrode fingers. The wide band gap substrate is sensitive to UV light, which can cause a conductivity change in the substrate. The electrode fingers are configured to sense a difference in substrate conductivity resulting from UV light. The detector has a fast response time, which enables it to detect Cherenkov light. The compact detector provides savings on size, weight, and required power. Thus, the solid-state detector can be used to replace photomultiplier tubes in Cherenkov detectors. The features of the novel detector allow for an improved system to detect and monitor UV radiation, especially during deep space missions.

Wrbanek, John D.↗
NASA NTRS1994

High Performance InGaAs/GaAs Quantum Well Infrared Photodetectors

By increasing the quantum well barrier width, incorporating spacer layers between the contacts and the multi quantum well region, and optimizing the materials growth parameters, we have dramatically reduced the dark current by many orders of magnitude and thereby significantly increased the detectivity.

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