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Highly efficient, low energy, low light level imagers and photodetectors are provided. In particular, a novel class of Della-Doped Electron Bombarded Array (DDEBA) photodetectors that will reduce the size, mass, power, complexity, and cost of conventional imaging systems while improving performance by using a thinned imager that is capable of detecting low-energy electrons, has high gain, and is of low noise.
We have designed plasmonic filters that simultaneously perform wavelength and polarization filtering in the wavelength range 3-5 micrometers. In this work we outline the design and present the simulated results of our filters. The filters consist of sub wavelength slits in a thin metal sheet which is deposited on top of a gallium antimonide (GaSb) substrate and a spacer layer of SiO2. This configuration makes our filters suitable for integration with GaSb based infrared photodetectors and photodetector arrays that are used in space applications. Our work opens up the possibility of using these detector arrays for highly compact Earth-observing infrared polarimeters and multispectral imaging applications.
Development of a hand-held long wavelength infrared (LWIR) camera at the Jet Propulsion Laboratory demonstrates the potential of quantum well infrared photodetector (QWIP) technology for simplifying the design and construction of a highly sensitive infrared imaging system.
Copper oxide compounds (Cu x O) with bandgaps of 1.3–2.1 eV (CuO) and 2.1–2.6 eV (Cu 2 O) have been investigated as promising p-type semiconducting materials. Cu x O is generally obtained by deposition or thermal oxidation, but those methods are not optimal for flexible substrates. Furthermore, additional patterning steps are required to fabricate devices. In this work, we present an easy, controllable method to fabricate a metal-semiconductor-metal (MSM) photodetector using laser-induced oxidation of a thin Cu film. After laser irradiation, the Cu film is heated under ambient conditions, and this leads to a thermal oxidation reaction, in which Cu oxide is monolithically formed in the Cu film and a Cu-Cu x O-Cu MSM structure is produced. Since the laser offers localized heating, an arbitrary CuxO pattern can be written in the Cu film by spatially controlled heating. In addition, by optimizing the heating time, the laser-induced oxidation can be successfully performed even on a flexible substrate. To study the laser-induced oxidation, we examined the correlation between laser parameters and the oxidation pattern and analyzed the composition using scanning electron microscopy, Raman spectroscopy, and X-ray photoemission spectroscopy. Furthermore, we measured the transient photoresponse and employed scanning photocurrent microscopy to investigate the mechanism of carrier transport behavior.
Film morphology of donor:acceptor blend layers plays a critical role in photon-to-current efficiency and dark/noise current of organic photodetectors (OPDs). One effective approach to manipulate crystallization and mesoscale phase separation of such blend layers is sequential casting (SC). However, the guiding strategies to control the morphology and the impacts on OPD performance of the SC films remain elusive, as the film structural evolution during SC is different from conventional blend casting (BC). In this report a refined fibrillar multiphase morphology is demonstrated by SC in an NT812:IEICO-4F blend film, where the high-quality IEICO-4F crystallites infiltrate the robust NT812 fibril network from the surface to the bulk. Such a morphology leads to improved charge generation and collection, reduced trap states, and enhanced charge block capability of resultant device, enabling simultaneous achievement of high external quantum efficiency and low dark/noise current. A maximum special detectivity of 5 × 10 13 Jones is achieved at 860 nm under –0.1 V, which is among the highest detectivities for vis-to-NIR OPDs. The linear dynamic range and response speed are also improved. Such enhancements are parallelly observed from OPD devices based on other blend systems with similar fibrillar refinement, which provides guidelines for film structure manipulation towards high OPD performance.
We report shape and dimensionality control by ligands is an efficient way to fabricate high-quality perovskite nanocrystals (NCs) with optoelectronic properties. Herein, to realize oriented transformations between different morphologies of CsPbBr 3 nanocrystals, we conceived of the use of defects and bidentate ligands to synergistically drive the reorientation of CsPbBr3nanocrystals into CsPbBr 3 nanowires (NWs). By employing aminocaproic acid as the bidentate ligand, CsPbBr 3 NWs were reconstructed from the CsPbBr 3 NCs (~7 nm) with 20-60 nm in width and several micrometers in length, as well as a 527 nm photoluminescence (PL) peak, 59% PL quantum yield, and 98.5 ns PL lifetime. The bidentate ligand-directed anisotropic shape evolution and growth of perovskite NWs from NCs was elucidated by transmission electronmicroscopy and PL studies. The photodetectors fabricated with the reconstructed CsPbBr 3 NWs displayed a photocurrent enhancement (2.75 × 10 -11 A) compared with that of the devices based on solution-synthesized NWs (2.28 × 10 -11 A). The device also showed a short response time, indicating its more sensitive photoelectric response. This process provides a viable approach to engineering diverse morphologies of perovskite nanocrystals for optoelectronic applications.
A number of applications in basic science and technology would benefit from high-fidelity photon-number-resolving photodetectors. While some recent experimental progress has been made in this direction, the requirements for true photon number resolution are stringent, and no design currently exists that achieves this goal. Here we employ techniques from fundamental quantum optics to demonstrate that detectors composed of subwavelength elements interacting collectively with the photon field can achieve high-performance photon number resolution. We propose a new design that simultaneously achieves photon number resolution, high efficiency, low jitter, low dark counts, and high count rate. Finally, we discuss specific systems that satisfy the design requirements, pointing to the important role of nanoscale device elements.
The performance of amorphous selenium (a-Se) as a cryogenic photodetector material is evaluated through a series of experiments using laterally structured devices operated in a custom optical test stand. These studies investigate the response of a-Se detectors to low-photon fluxes at high electric fields near avalanche conditions, the linearity of the photoconductive response over a wide dynamic range and the direct detection of narrowband 130 nm vacuum ultraviolet (VUV) illumination. At 87 K, matched-filter analysis shows reliable single-shot detection with efficiencies ≥80% and area under the curve (AUC) ≥ 0.85 using as few as ∼ 6800 incident 401 nm photons, corresponding to ∼ 3400 photons within field-active regions after accounting for geometric constraints. Measurements are performed at cryogenic temperatures using calibrated photon fluxes derived from a silicon photomultiplier reference and a characterized optical filter stack. Additional experiments using a tellurium-doped a-Se (a-SeTe) device explore the material's behavior under identical test conditions and demonstrate that avalanche is achievable in a-SeTe at cryogenic temperatures. The results demonstrate reproducible low-noise operation, VUV sensitivity and field-dependent gain behavior in a lateral a-Se architecture, representing the first reported observation of avalanche multiplication in laterally structured a-Se and a-SeTe devices at cryogenic temperatures. These findings support the potential integration of laterally structured a-Se devices into next-generation pixelated liquid-argon time projection chambers (TPCs) requiring scalable, high-field-compatible photon detection systems.
Here, aluminum-gallium-nitride photodetectors were successfully fabricated with micrometer-scale metal–semiconductor–metal structures and tested with ultrafast, UV laser pulses. The measurements were performed with single-shot oscilloscopes. Pulse-broadening effects caused by the measurement system were systematically evaluated and reduced to resolve the intrinsic response time of the detector. The best-performing devices showed a response time of below 25 ps and dark currents below 20 pA. The devices showed linear response with the bias voltage and the laser energy
A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD’s emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30–60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 10 14 cm –2 dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells.
Spectrally selective photodetectors for the middle and vacuum ultraviolet
Spectrally selective photodetector for middle and vacuum ultraviolet
Characteristics of vacuum deposited thin film cadmium sulfide photodetectors for space navigation
We have demonstrated red-shifting of the wavelength response of a bound-to-continuum p-type ultra-thin InGaAs/Inp quantum well infrared photodetector after growth via rapid thermal annealing. Compared to the as-grown detector, the peak spectral response of the annealed detector was shifted to longer wavelength without any major degradation in responsivity characteristics.
In this paper, we discuss the development of very sensitive long wavelength infrared (LWIR) GaAs/AlGal-xAs Quantum well infrared photodetectors (QWIPS), fabrication of random reflectors for efficient light coupling, and the demonstration of a LWIR 256 X 256 focal plane array imaging camera. Excellent imagery, with a noise equivalent differential temperature (NE-delta-T) of 25 mK has been achieved.
Long wavelength infrared (LWIR) detectors, 8 (micro)m to 12 (micro)m, are of great interest for a variety of ground-based and space-borne applications. These applications have placed stringent requirements on the performance of the infrared detectors and arrays including high detectivity, low dark current, uniformity, radiation hardness, and low power dissipation. I will discuss the development and progress of GaAs based long-wavelength quantum well infrared photodetectors (QWIPs) to meet those stringent requirements and the demonstration of a 9 (micro)m cutoff 640x480 QUIP focal plane array camera. The noise equivalent temperature difference of the focal plane array is 25 mK at 300 K background and the operating temperature is 70 K.
A 9 (micro)m 256x256 hand-held quantum well infrared photodetector (QWIP) camera has been demonstrated. Excellent imagery, with a noise equivalent differential temperature (NE(gamma)) of 26 mK has been achieved. In this presentation, we discuss the development of this very sensitive long wavelength infrared (LWIR) camera based on a GaAs/AlGaAs QWIP focal plane array, its performance in quantum efficience, NA(gamma), minimum resolvable temperature (MRTD), uniformity, operability, and its applications.