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NASA NTRS2024

SiC Charged Particle Telescope GRC Independent Research and Development (IRAD) Program End of Project Final Report

In an advancement over the state-of-the art, NASA Glenn Research Center (GRC) has developed a large area silicon carbide (SiC)-based charged particle telescope through an Independent Research and Development (IRAD) project. The telescope has been demonstrated to have improved noise characteristics and resolution than previous SiC detectors. This improvement will meet the challenges of compact multidirectional robust radiation detector systems to study a wide range of elementary particle mass and energies. In order to provide a complete understanding of how energetic processes internal and external to the solar system shape magnetospheres, atmospheres, and surfaces, in situ particle observations should include measurements of Solar Energetic Particles (SEP) and Galactic Cosmic Rays (GCR), along with solar wind and plasma. The potential temperature stability, tolerance to high radiation environments, and low noise characteristics expected in SiC-based detectors can have advantages over the state-of-the-art silicon detectors. These advantages will allow the detectors to be deployed in small compact systems on a variety of platforms, enabling compact structures for small satellite platforms with improved data quality.

Field and particle detectors↗

DOE OSTI2021

Detecting ionizing radiation using halide perovskite semiconductors processed through solution and alternative methods

We report the direct detection of high-energy radiation such as X-rays and.-rays by semiconductors at room temperature is a challenging proposition that requires remarkably pure and nearly perfect crystals. The emergence of metal halide perovskites, defect-tolerant semiconductors, is reviving hope for new materials in this field after an almost 20 year hiatus. Metal halide perovskites, which combine exceptional optoelectronic properties, versatile chemistry and simple synthesis, are challenging traditional approaches for the development of novel semiconductors for detecting hard radiation. We discuss the relevant physical properties, promising materials, fabrication techniques and device architectures for high-performance, low-cost detectors by targeting next-generation semiconductors for radiation detection. We also present a perspective on the impact of such advances in future medical imaging applications.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Effect of the Electric Field Strength on the Energy Resolution of Cr/CdTe/Pt Detectors

The electrical and spectrometric characteristics of the Cr/cadmium telluride (CdTe)/Pt structure with a metal-semiconductor type rectifying contact, used in X/γ-ray detectors, are investigated. For the detectors fabrication, chlorine-doped CdTe crystals with a resistivity of (3-6) × 10 9 Ω cm at 293 K were used. 137Cs spectra and their modification by applied voltage change were obtained. The reverse bias voltage corresponding to the best energy resolution of the Cr/CdTe/Pt structure is experimentally determined. The concentration of impurities N in the crystal, which determines the thickness of the space-charge region, is estimated. Finally, an energy resolution deterioration of the Cr/CdTe/Pt structure with increasing voltage is explained due to the Gunn effect.

47 OTHER INSTRUMENTATION↗

NASA NTRS1991

Multiple-Quantum-Well Intersubband Infrared Detector

Proposed multiple-quantum-well intersubband semiconductor device detects photons over broader range of wavelengths. Device is stack of substacks, each of which contains quantum-well layers sensitive to different narrow band of wavelengths. Bandwidth and detectivity increased.

Borenstain, Shmuel I.↗

DOE OSTI2024

Role of Selenium in CdZnTeSe as a Defect Engineering Agent

Cadmium zinc telluride (CdZnTe) with 10 atomic % Zn has been the material of choice for room-temperature semiconductor compact X- and gamma-ray detector applications for over three decades. Despite its commercial success as the most desirable room-temperature semiconductor radiation detection material, CdZnTe (CZT) suffers from a lack of compositional homogeneity on both the micro- and macroscales and the presence of high concentrations of performance-limiting defects such as subgrain boundary networks (dislocation walls) and secondary phases (Te-rich inclusions). Random distributions of these defects in the CZT matrix result in the spatial inhomogeneity of the material’s charge-transport properties. The recently discovered quaternary Cd x Zn 1-x Te 1-y Se y (CZTS) has experienced remarkable advances in its material properties, with highly reduced defects and higher compositional homogeneity. This book chapter focuses on the presence of performance-limiting defects in CZT that have thus far hindered the yield and cost of high-quality detectors and restricted their widespread deployment for a variety of potential applications, particularly for their use as large-volume gamma detectors, where the demands on material perfection are significantly greater. This chapter also provides an overview of the recent developments in the quaternary material CZTS, particularly the effects of selenium (Se) in the CZTS matrix on the defect engineering of the quaternary alloy material and the advancement of CZTS as a potential next-generation detector operable at room temperature.

Roy, Utpal N.↗

DOE OSTI2022

Vertical gradient freeze growth of detector grade CdZnTeSe single crystals

Here, we report the growth of detector grade Cd 0.9 Zn 0.1 Te 0.97 Se 0.03 (CZTS) single crystals, a recently discovered quaternary semiconductor for room temperature radiation detection, by a vertical gradient freeze (VGF) method. VGF is a comparatively low-temperature growth method and avoids relative motion between the heater and the ampoule containing the precursor materials which minimizes any thermal drift or temperature fluctuations. As a result, CZTS single crystals with superior charge transport properties has been obtained. Growth of detector-grade CZTS single crystals using VGF method has not been reported yet. X-ray spectroscopy based elemental analysis showed that the grown crystals demonstrated the desired stoichiometry required for high resolution radiation detection. Planar detectors fabricated by deposition of gold contacts (~0.07 cm 2 ) demonstrated high bulk resistivity ~10 10 Ω-cm and a very low leakage current density of 2.8 × 10 –8 A/cm 2 at a bias of 100 V when measured at room temperature. The detectors showed excellent radiation response with 100 % charge collection efficiency when exposed to 5486 keV alpha particles. The electron mobility-lifetime (μτ) product was measured to be 3 × 10 –3 cm 2 /V using a single polarity Hecht analysis which is at par with the recently reported values measured in CZTS grown using conventional Bridgman or travelling heater method. The electron mobility has been calculated to be 964 cm 2 V –1 s –1 using a time-of-flight (TOF) method, a substantial improvement over that obtained from conventionally grown CZTS single crystals.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Dynamically Tunable Terahertz Emission Enabled by Anomalous Optical Phonon Responses in Lead Telluride

Lead telluride (PbTe), a narrow bandgap semiconductor commonly used in infrared detectors, exhibits anomalous vibrational and structural properties, making it appealing for thermoelectrics. Despite significant fundamental interest in the microscopic origins of its unusual vibrational properties, the optical functionalities stemming from phonons and electron–phonon coupling in PbTe have not been closely investigated. This work reports measurements of terahertz (THz) radiation from a PbTe single crystal following ultrafast optical excitation and investigates IR-active phonon responses as a function of excitation fluence and temperature. We uncover a spectrally tunable THz emission peak enabled by an epsilon-near-zero response of the coupled plasmon–longitudinal optical phonon mode that can be dynamically shifted via tuning photocarrier density. Spectral tunability (Δω/ω = 25%) is significant and beyond what has been achieved by any other THz emitter. In addition, the emitted THz fields reveal signatures of a zone center transverse optical phonon anomaly and unveil a new mode at 0.3 THz that diminishes in amplitude under increasing photocarrier density. Temperature-dependent measurements suggest that the transverse-like modes at 1 and 1.5 THz are possibly of different origins. These results indicate that the unusual phononic properties in PbTe are tunable via photoexcitation and enable new optical functionalities in THz applications, such as spectrally tunable emitters and all-optical modulators.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Parameters of fast and high-yield InAs/GaAs quantum dot semiconductor scintillator

InAs quantum dots (QDs) embedded into a waveguiding GaAs semiconductor matrix may produce scintillation detectors with exceptional speed and yield, making them valuable for nuclear security, medical imaging, and high energy physics applications. In this work, we developed thick (~25 μm) epitaxial heterostructres with high luminescence efficiency composed of self-assembled nano-engineered InAs QDs grown by molecular beam epitaxy. Here, the bulk GaAs acts as a stopping material for incident particles and as a waveguide when layer-transferred onto a low-index substrate. Waveguiding and self-absorption (< 1 cm –1 ) were studied using photoluminescence with scanning laser excitation and modeled with ray optics approximation and geometrical coupling of high-index waveguide to a collection fiber. Scintillating signals from α-particles were analyzed with an external photodiode (PD) and an integrated PD which provided an improved optical coupling. The mean charge collected by the integrated PD corresponded to 3 × 10 4 photoelectrons per 1 MeV of deposited energy, or ~13% of the theoretically achievable light yield. Combined with the previously measured QD scintillation time of 0.3-0.6 ns, this makes the InAs/GaAs QD heterostructures the fastest high yield scintillation material reported.

36 MATERIALS SCIENCE↗

NASA NTRS1976

Chemical Analysis of Outgassing Contaminants on Spacecraft Surfaces

Samples of S-13 paint on aluminum, reflection grating anomalies as affected by dielectric coatings, and rocket effluents were analyzed along with Skylab window scrapings and a gas activated semiconductor. Development of an HCl detector is also discussed. Results are briefly summarized.

Mcnutt, R. C.↗

NASA NTRS1986

Measuring Thermal Diffusivity of Molten Semiconductors

Thermal diffusivity of molten and solid mercury cadmium telluride measured with aid of new apparatus. Knowledge gained from such measurements help efforts to grow high-quality single crystals of this semiconductor for use in infrared detectors: Without knowledge of thermal diffusivity, difficult to control growth rate of solid from molten material.

Crouch, R.↗

NASA NTRS2005

Multi-Band and Broad-Band Infrared Detectors Based on III-V Materials for Spectral Imaging Instruments

Quantum well infrared photodetector technology has shown remarkable success by realizing large-format focal plane arrays in both broad-bands and in multi-bands. The spectral response of these detectors based on the III-V material system are tailorable within the mid and long wavelength IR bands (similar to 3-25 mu m) and possibly beyond. Multi-band and broad-band detector arrays have been developed by vertically integrating stacks of multi quantum wells tailored for response in different wavelengths bands. Each detector stack absorbs photons within the specified wavelength band while allowing the transmission other photons, thus efficiently permitting multiband detection. Flexibility in many design parameters of these detectors allows for tuning and tailoring the spectral shape according to application requirements, specifically for spectral imaging instruments.

quantum well devices↗

NASA NTRS2016

Fine-Pitch CdTe Detector for Hard X-Ray Imaging and Spectroscopy of the Sun with the FOXSI Rocket Experiment

We have developed a fine-pitch hard X-ray (HXR) detector using a cadmium telluride (CdTe) semiconductor for imaging and spectroscopy for the second launch of the Focusing Optics Solar X-ray Imager (FOXSI). FOXSI is a rocket experiment to perform high sensitivity HXR observations from 4 to 15 keV using the new technique of HXR focusing optics. The focal plane detector requires less than 100 micrometers position resolution (to take advantage of the angular resolution of the optics) and approximately equals 1 keV energy resolution (full width at half maximum (FWHM)) for spectroscopy down to 4 keV, with moderate cooling (greater than -30 C). Double-sided silicon strip detectors were used for the first FOXSI flight in 2012 to meet these criteria. To improve the detectors' efficiency (66% at 15 keV for the silicon detectors) and position resolution of 75 micrometers for the second launch, we fabricated double-sided CdTe strip detectors with a position resolution of 60 micrometers and almost 100% efficiency for the FOXSI energy range. The sensitive area is 7.67 mm x 7.67 mm, corresponding to the field of view of 791'' x 791''. An energy resolution of 1 keV (FWHM) and low-energy threshold of approximately equals 4 keV were achieved in laboratory calibrations. The second launch of FOXSI was performed on 11 December 2014, and images from the Sun were successfully obtained with the CdTe detector. Therefore, we successfully demonstrated the detector concept and the usefulness of this technique for future HXR observations of the Sun.

Ishikawa, Shin-nosuke↗

NASA NTRSDate not supplied

Wide Band Gap Radiation Detectors for Deep Space Science

Understanding how the Sun, Earth, and other objects in the solar system interact with the space radiation environment is crucial for improving activities of humans on Earth and in space. Low-power, low-noise, multidirectional robust detectors for detecting ions with a wide range of mass and energies will provide a more complete understanding of space environment physics. To meet these challenges, new ion detectors based on wide band gap (WBG) semiconductors are being developed for integration on a variety of deep space platforms. NASA Glenn Research Center (GRC) is applying its expertise and facilities in harsh environment instrumentation to develop supporting technologies to enable improved instruments for space science missions. New detector technologies being developed at GRC include SiC solid-state devices as practical robust, thermally stable large area detectors for LET measurements in compact, stacked charged particle telescope. The low-noise, thermally stable nature of the WBG detectors allows a small multidirectional array of charged particle telescopes to be packed in a 6U CubeSat without active cooling for operation in lunar orbit or deep space. Using a full variety of different WBG detectors, an extremely compact instrument to provide multi-directional, comprehensive (composition, velocity, and direction) in-situ measurements of heavy ions in space plasma environments can be realized.

ion detectors↗

DOE OSTI2021

Quaternary Semiconductor Cd1−xZnxTe1−ySey for High-Resolution, Room-Temperature Gamma-Ray Detection

The application of Cd0.9Zn0.1Te (CZT) single crystals, the primary choice for high-resolution, room-temperature compact gamma-ray detectors in the field of medical imaging and homeland security for the past three decades, is limited by the high cost of production and maintenance due to low detector grade crystal growth yield. The recent advent of its quaternary successor, Cd0.9Zn0.1Te1−ySey (CZTS), has exhibited remarkable crystal growth yield above 90% compared to that of ~33% for CZT. The inclusion of Se in appropriate stoichiometry in the CZT matrix is responsible for reducing the concentration of sub-grain boundary (SGB) networks which greatly enhances the compositional homogeneity and growth yield. SGB networks also host defect centers responsible for charge trapping, hence their reduced concentration ensures minimized charge trapping. Indeed, CZTS single crystals have shown remarkable improvement in electron charge transport properties and energy resolution over CZT detectors. However, our studies have found that the overall charge transport in CZTS is still limited by the hole trapping. In this article, we systematically review the advances in the CZTS growth techniques, its performance as room-temperature radiation detector, and the role of defects and their passivation studies needed to improve the performance of CZTS detectors further.

36 MATERIALS SCIENCE↗

NASA NTRS1991

Long-wave infrared (LWIR) detectors based on III-V materials

Future NASA missions for earth observation and planetary science require large photovoltaic detector arrays with high performance in the long wavelength region to 18 microns and at operating temperatures above 65 K where single-cycle long-life cryocoolers are being developed. Since these detector array requirements exceed the state of current HgCdTe technology, alternative detector materials are being investigated as a possible option for future missions. Advanced growth techniques (e.g., MBE and MOCVD) of column III-V semiconductors have opened opportunities for engineering new detector materials and device structures. The technical approaches under investigation at JPL (with university and industry participation) include: quantum well infrared photodetectors, heterojunction internal photoemission (HIP) photodetectors, type-II strained layer superlattices, and nipi doping superlattices. Each of these options are briefly described with some of their pros and cons. A more detailed description is given for the HIP approach being pioneered at JPL.

Maserjian, Joseph↗

DOE OSTI2022

Active Region Extent Assessment with X-rays (AREA-X)

The development of semiconductor sensors for new particle tracking detectors places increasing limits on sensor characteristics such as uniformity, size and shape of inefficient areas and size of active compared to inactive sensor areas. Accurately assessing these relatively subtle effects requires either measurements in particle beams or the modification of samples to be used in dedicated laser test setups. Active Region Extent Assessment with X-rays (AREA-X) has been developed as an alternative method for the fast, efficient and precise study of the active area of a semiconductor sensor. It uses a monochromatic, micro-focused X-ray beam with a 10–20 keV energy range as provided by several synchrotron beam lines and uses the photo current induced in the sensor to measure the depth of the responsive sensor volume. It can be used to study local inhomogeneities or inefficiencies, the overall extent of the active sensor volume and its shape and its localised application, which makes the need to gather statistics over a large area unnecessary, allowing for fast readout, which enables studies of the sensor behaviour at a range of external parameters, e.g. temperature or applied bias voltage. This paper presents the measurement concept and technical setup of the measurement, results from initial measurements as well as capabilities and limitations of the method.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

The Role of Metal-Semiconductor Interface in Hybrid Perovskite Devices for High-Performance Radiation Photon Counting

Halide perovskites are promising optoelectronic semiconductors. For applications in solid-state detectors that operate in low photon flux counting mode, blocking interfaces are essential to minimize the dark current noise. Here, we investigate the interface between methylammonium lead tri-iodide (MAPbI 3 ) single crystals and commonly used high and low work function metals to achieve photon counting capabilities in a solid-state detector. Using scanning photocurrent microscopy, we observe a large Schottky barrier at the MAPbI 3 /Pb interface, which efficiently blocks dark current. Moreover, the shape of the photocurrent profile indicates that the MAPbI 3 single-crystal surface has a deep fermi level close to that of Au. Rationalized by first-principle calculations, we attribute this observation to the defects due to excess iodine on the surface underpinning emergence of deep band-edge states. The photocurrent decay profile yields a charge carrier diffusion length of 10–25 μm. Using this knowledge, we demonstrate a single-crystal MAPbI 3 detector that can count single γ-ray photons by producing sharp electrical pulses with a fast rise time of <2 μs. Overall, our study indicates that the interface plays a crucial role in solid-state detectors operating in photon counting mode.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Lithium indium diselenide — An advanced material for neutron detection

Here, this paper describes the synthesis, crystal growth, detector fabrication, radiation hardening studies, MCNP modeling, and characterization of lithium indium diselenide or LiInSe 2 . This newly-developed room temperature thermal neutron detector has semiconducting and scintillating properties and it is suitable for neutron detection application. LiInSe 2 was synthesized starting from elemental Li, In, Se in two steps due to high reactivity of Li. A single crystal of LiInSe 2 was grown using the Vertical Bridgman method. The room temperature band gap was found to be 2.8 eV using optical absorption measurements. Bulk resistivity was measured at ∼5 × 10 11 Ωcm. Photoconductivity measurements of LiInSe 2 wafers identified a peak in the photocurrent around 445 nm. Nuclear radiation detectors were fabricated from single crystal wafer and the responses to alpha particles at various biases were measured. The mobility-lifetime product was estimated. Gamma irradiation studies were performed with calculated absorbed doses ranging from 0.2126 to 21,262 Gy. The characterization of the two wafers for their scintillator performance was conducted after each irradiation. The gamma irradiation produced a reduction of the light yield that translated to a lower channel number for the centroid of alpha detection spectra. It also showed a considerable reduction of the decay time after the first irradiation. These are the first studies on gamma radiation hardening with this material.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗