L. Faraone

University of Western Australia, Perth City, Western Australia, Australia

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Publications (406)470.04 Total impact

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    ABSTRACT: This paper reports on a proof-of-concept micro-electromechanical system-based Fabry-Perot filter that is capable of electrically tuning within the long-wave infrared thermal imaging band of 8-12 μm. The device employs a single-layer quarter-wavelength thick tensile germanium membrane for the suspended top mirror in order to achieve nanometer-scale as-released mirror flatness across an area of several hundred square micrometers without any extraneous stress management techniques. Mechanical and optical characterization of the tunable filters of various sizes are presented and compared. A 200-μm dimension square filter is demonstrated with <100-nm top mirror bowing and near-theoretical spectral characteristics across the entire tuning range of 8.5-11.5 μm, namely, peak transmission above 80%, full-width at half-maximum of spectral passband of approximately 500 nm, and out-of-band rejection greater than 40:1. Optical modeling shows that this filter can achieve a pixel-to-pixel transmission peak wavelength variation of less than 1.2% across the entire 200 μm x 200-μm optical imaging area. These results exceed the optical performance requirements for passive multispectral thermal imaging applications based on large-area focal plane arrays. In comparison, the 500 and 1000-μm dimension filters are shown to exhibit significant mirror bowing with actuation and, thus, for a pixel-to-pixel transmission peak wavelength non-uniformity of < 4%, demonstrate narrower usable spectral tuning ranges of 9.3-11.4 and 10.3-11.3 μm, respectively. [2015-0252]
    No preview · Article · Jan 2016 · Journal of Microelectromechanical Systems
  • Wen Lei · Jarek Antoszewski · Lorenzo Faraone
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    ABSTRACT: This article presents a review on the current status, challenges, and potential future development opportunities for HgCdTe infrared materials and detector technology. A brief history of HgCdTe infrared technology is firstly summarized and discussed, leading to the conclusion that HgCdTe-based infrared detectors will continue to be a core infrared technology with expanded capabilities in the future due to a unique combination of its favourable properties. Recent progress and the current status of HgCdTe infrared technology are reviewed, including material growth, device architecture, device processing, surface passivation, and focal plane array applications. The further development of infrared applications requires that future infrared detectors have the features of lower cost, smaller pixel size, larger array format size, higher operating temperature, and multi-band detection, which presents a number of serious challenges to current HgCdTe-based infrared technology. The primary challenges include well controlled p-type doping, lower cost, larger array format size, higher operating temperature, multi-band detection, and advanced plasma dry etching. Various new concepts and technologies are proposed and discussed that have the potential to overcome the existing primary challenges that are inhibiting the development of next generation HgCdTe infrared detector technology.
    No preview · Article · Dec 2015 · Applied Physics Reviews
  • I. Madni · G. A. Umana-Membreno · W. Lei · R. Gu · J. Antoszewski · L. Faraone
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    ABSTRACT: The minority carrier lifetime in molecular beam epitaxy grown layers of iodine-doped Hg1-xCdxTe (x ∼ 0.3) on CdZnTe substrates has been studied. The samples demonstrated extrinsic donor behavior for carrier concentrations in the range from 2 × 1016 cm-3 to 6 × 1017 cm-3 without any post-growth annealing. At a temperature of 77 K, the electron mobility was found to vary from 104 cm2/V s to 7 × 103 cm2/V s and minority carrier lifetime from 1.6 μs to 790 ns, respectively, as the carrier concentration was increased from 2 × 1016 cm-3 to 6 × 1017 cm-3. The diffusion of iodine is much lower than that of indium and hence a better alternative in heterostructures such as nBn devices. The influence of carrier concentration and temperature on the minority carrier lifetime was studied in order to characterize the carrier recombination mechanisms. Measured lifetimes were also analyzed and compared with the theoretical models of the various recombination processes occurring in these materials, indicating that Auger-1 recombination was predominant at higher doping levels. An increase in deep-level generation-recombination centers was observed with increasing doping level, which suggests that the increase in deep-level trap density is associated with the incorporation of higher concentrations of iodine into the HgCdTe.
    No preview · Article · Nov 2015 · Applied Physics Letters
  • J. Antoszewski · N. D. Akhavan · G. Umana-Membreno · R. Gu · W. Lei · L. Faraone

    No preview · Article · Oct 2015 · ECS Transactions
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    ABSTRACT: This letter presents the design, fabrication, and optical characterization of silicon-air-silicon-based surface micro-machined distributed Bragg reflectors (DBRs) for the visible to near infrared wavelength range (540–960 nm). The DBR (mirror) consisted of two quarter wave thick silicon films separated by a quarter-wave air gap. A mirror array was successfully fabricated, consisting of mirrors ranging in diameter between 270 and 420 $mu text{m}$ . Calibrated optical measurements indicate that a peak reflectivity close to 92% has been achieved for visible wavelengths, despite the fact that silicon has strong absorbtion in the visible wavelength range. The mirrors are shown to be broadband reflectors, having 85% or more reflectivity over a 160-nm wavelength range. A spatially resolved optical transmission mapping and optical transmission profile of the mirrors demonstrates high uniformity across the fabricated array of DBRs. [2015-0140]
    Full-text · Article · Oct 2015 · Journal of Microelectromechanical Systems
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    ABSTRACT: We present the design, fabrication, and optical characterization of silicon-air-silicon-based distributed Bragg reflectors, or quarter wavelength mirrors, in sizes ranging from 200 ?m x 200 ?m to 5 mm x 5 mm. Such mirrors can be used in conjunction with either single-element photodetectors or large-area focal plane arrays to realize tunable multispectral sensors or adaptive focal plane arrays from the short-wave infrared wavelength ranges (1500-3000 nm) to mid-wave infrared wavelength (3000-6000 nm) ranges. Surface optical profile measurements indicate a flatness of the order of 20-30 nm in the fabricated structures across several millimetres. Single point spectral measurements on devices show excellent agreement with simulated optical models. The fabricated distributed Bragg reflectors show ~94% reflectivity, which is in close agreement with theoretical reflectivity. The demonstrated high reflectivity across a wide wavelength range renders them suitable as broadband reflectors. Finally, we present optical transmittance modeling results for Fabry-P?rot filters based on these distributed Bragg reflectors. [2015-0161]
    Full-text · Article · Sep 2015 · Journal of Microelectromechanical Systems
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    ABSTRACT: Thermally evaporated n-type CdS thin films were studied to determine the influence of substrate deposition temperature and postdeposition thermal annealing on their electrical, optical, and structural properties. It is shown that although increasing substrate temperature during deposition from room temperature to 200 $^{circ }$C results in CdS films exhibiting high optical transmittance as well as large grain size, deposition temperatures above 50 $^{circ }$ C lead to significant degradation in carrier concentration and mobility. Postdeposition thermal annealing of CdS films deposited at room temperature is shown to yield CdS films with superior electrical and optical characteristics, resulting in an electron mobility of 17.45 cm$^{2}$/Vs for films annealed at 200 $^{circ }$C. The electrical characteristic of n-CdS/p-Si heterojunction diodes indicated that postdeposition thermal annealing reduced parasitic series resistance and decreased the diode ideality factor to a value of 1.384 for films annealed at 300 $^{circ }$C, suggesting a reduction in recombination centers in the vicinity of the CdS/Si interface. In n-CdS/p-CdTe heterojunction solar cells, the photovoltaic cell parameters indicated that the deposition of CdS films at room temperature produces better performing cells with the substrate temperature required during the thermal deposition of CdTe acting as postdeposition annealing for the underlying CdS thin film.
    No preview · Article · Sep 2015 · IEEE Journal of Photovoltaics
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    ABSTRACT: This paper reports on the successful demonstration of Ge/ZnS-based Fabry-Perot filters operating in the longwave infrared (LWIR). The suitability of thermally deposited Ge and ZnS as thin-film mirror materials for micromachined LWIR Fabry-Perot filters has been fully investigated, and it is shown that a film growth temperature higher than 150 °C is key to depositing durable ZnS films. The optical constants of Ge and ZnS films in the LWIR band reveal that the material pair possesses high refractive index contrast and excellent LWIR transparency. Fixed-cavity LWIR Fabry-Perot filters with a 150-μm circular single-layer Ge top mirror and a four-layer Ge/ZnS/Ge/ZnS bottom mirror were fabricated. Curvature in the suspended top mirror was corrected using a thin SiNₓ stress-compensation layer. After curvature correction, a mirror flatness of 550 nm was achieved, and the filter demonstrated a 60% peak transmission with a full-width at half-maximum of 700 nm as well as a out-of-band rejection of 24:1. [2015-0143]
    No preview · Article · Sep 2015 · Journal of Microelectromechanical Systems
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    ABSTRACT: Recent experimental results have demonstrated the possibility of characterizing silicon-on-insulator (SOI) wafers through split – measurements in the pseudo-MOSFET configuration. This paper analyzes the capacitance and conductance versus frequency characteristics. We discuss the conditions under which it is possible to extract interface trap density in bare SOI wafers. The results indicate, through both measurements and simulations, that the signature due to interface trap density is present in small-area samples, but is masked by the response of the channel in regular, large-area ones, making the extraction in standard samples problematic.
    Full-text · Article · Sep 2015 · IEEE Transactions on Electron Devices
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    ABSTRACT: In this paper, we present the optimization of optical and mechanical properties of inductively coupled plasma chemical vapor deposited (ICPCVD) amorphous silicon thin films for fabrication of high-quality optical microelectromechanical systems-based devices operating from visible to short-wave infrared wavelengths (450-3000 nm). Our results indicate that, at relatively high deposition temperatures for plasma CVD, a decrease in the ICP power results in films with lower tensile stress, higher refractive index, and lower extinction coefficient. We show that hydrogen concentration alone is not a sufficient parameter for controlling optical and mechanical quality of the films. In particular, both the hydrogen concentration and the hydrogen-silicon bonding nature together play a vital role in determining the optical and the mechanical quality of the silicon thin films. As a demonstration vehicle, three layer silicon-silicon oxide-silicon-based distributed Bragg reflectors were fabricated for the visible (500-700 nm), near infrared (700-1000 nm), and short-wave infrared (2000-3000 nm) wavelength ranges using an optimized silicon fabrication recipe. The measured optical transmission spectra show close to 90% peak reflectivity. Finally, stress optimization was evaluated by fabricating 270-μm diameter circular suspended silicon membranes, which demonstrate a flatness variation on the order of <6 nm across the entire lateral dimension. [2015-0029]
    No preview · Article · Aug 2015 · Journal of Microelectromechanical Systems
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    ABSTRACT: We present the design, fabrication, and optical and mechanical characterization of silicon-/silicon-oxide-based optical filters and distributed Bragg reflectors in sizes ranging from to . They are designed to be used in conjunction with either single-element photodetectors or large-area focal plane arrays to realize tunable multispectral sensors or adaptive focal plane arrays in the shortwave infrared wavelength range. Surface optical profile measurements indicate a flatness of the order of 30 nm in the fabricated structures across several millimeters. Single-point spectral measurements on devices show an excellent agreement with simulated optical models, and demonstrate Si-SiOx-Si fixed optical filters with a 94% transmission at 1940 nm with a full-width at half-maximum of 250 nm. Distributed Bragg reflectors demonstrate 90% reflectance across the 1560–2050-nm wavelength range, making them suitable as broadband reflectors. The optical spatial uniformity across a 3-mm -mm device shows only a 3% variation across the entire optically active area. Finally, the mechanical resonance characteristic of a 1-mm -mm fabricated device shows the lowest resonant frequency of the suspended structure to be 39 kHz, indicating excellent immunity to extraneous low-frequency vibrations. [2014-0278]
    No preview · Article · Aug 2015 · Journal of Microelectromechanical Systems
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    W. Lei · R.J. Gu · J. Antoszewski · J. Dell · G. Neusser · M. Sieger · B. Mizaikoff · L. Faraone
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    ABSTRACT: GaSb has been studied as a new alternative substrate for growing HgCdTe via molecular beam epitaxy (MBE). Cross-sectional transmission electron microscopy (TEM) studies indicate that MBE-grown CdTe buffer layers on GaSb have much lower misfit dislocation density than comparable layers grown on GaAs. The MBE-grown mid-wave infrared (MWIR) HgCdTe layers on GaSb substrates present material quality comparable to those grown on GaAs substrates, which is one of the state-of-the-art alternative substrates currently used to grow HgCdTe for the fabrication of MWIR detectors and focal plane arrays. Typically, HgCdTe materials grown on GaSb are found to have a rocking curve (double crystal x-ray diffraction) full width at half maximum of ~122 arcsec and an etch pit density of ~mid-106 cm–2. Electron backscatter diffraction mapping shows that the lattice misorientation/misfit dislocations near the HgCdTe/CdTe interface are negligible for GaSb substrates in comparison to GaAs substrates, and that the material quality of the HgCdTe layer on GaSb is determined primarily by the material quality of the CdTe buffer layer. These preliminary results are very encouraging considering that this is a relatively recent research effort, and higher quality MBE-grown HgCdTe materials are expected on GaSb substrates with further optimization of HgCdTe growth conditions as well as further improvements in the growth conditions for CdTe buffer layers.
    Full-text · Article · Jun 2015 · Journal of Electronic Materials
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    ABSTRACT: Multi-carrier transport in planar fully-depleted silicon-on-insulator (FD-SOI) MOSFETs has been investigated employing magnetic-field dependent geometrical magnetoresistance measurements and high-resolution mobility spectrum analysis. The results indicate that electronic transport in the 10 nm thick Si channel layer is due to two distinct and well-defined electron species. Although self-consistent Schrödinger–Poisson numerical calculations indicate significant localization of the total electron population near the back and front interfaces, the results of mobility spectrum analysis suggest that the mobility distributions associated with these spatially localized populations are strongly coupled through carrier scattering processes, and do not have independent and distinguishable mobility distributions. The two detected electron mobility distributions are thus evidence of sub-band modulated transport in 10-nm thick Si planar FD-SOI MOSFETs. The mobility maximum of the dominant carrier was found to occur under gate bias conditions that result in a minimum perpendicular effective electric field.
    Full-text · Article · Jun 2015 · Solid-State Electronics
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    ABSTRACT: Magnetic-field dependent resistivity and Hall-effect measurements combined with high resolution mobility spectrum analysis (HR-MSA) were employed to study room-temperature electronic transport in 4H-SiC metal–oxide–semiconductor field-effect transistor (MOSFET) structures. It is shown that the mobility distribution for electrons at the SiO2/SiC interface is significantly broader than expected for quantum confined carriers, exhibiting Hall scattering factors significantly greater than the generally assumed unity value. The interfacial electron mobility and Hall scattering factor are likely to be determined by potential fluctuations arising from a disordered transition layer on the SiC side of the SiO2/SiC interface. For the MOSFET structures studied, charge trapping at the SiO2/SiC interface was found to determine the interfacial free electron sheet density, in agreement with prior studies on similar device structures. HR-MSA has enabled unambiguous discrimination between electrons in the ion-implanted buried channel layer and at SiO2/SiC interface in a depletion-mode MOSFET structure.
    Full-text · Article · Apr 2015 · Microelectronic Engineering
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    ABSTRACT: We report a theoretical study of mercury cadmium telluride (HgCdTe) unipolar n-type/barrier/n-type (nBn) detectors for midwave infrared (MWIR) applications at elevated temperatures. The results obtained indicate that the composition, doping, and thickness of the barrier layer in MWIR HgCdTe nBn detectors can be optimized to yield performance levels comparable with those of ideal HgCdTe p-n photodiodes. It is also shown that introduction of an additional barrier at the back contact layer of the detector structure (nBnn+) leads to substantial suppression of the Auger generation-recombination (GR) mechanism; this results in an order-of-magnitude reduction in the dark current level compared with conventional nBn or p-n junction-based detectors, thus enabling background-limited detector operation above 200 K.
    Full-text · Article · Apr 2015 · Journal of Electronic Materials
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    Full-text · Dataset · Mar 2015
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    Full-text · Dataset · Mar 2015
  • J. Zhang · G. A. Umana-Membreno · R. Gu · W. Lei · J. Antoszewski · J. M. Dell · L. Faraone
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    ABSTRACT: In this paper, we report results of a study of SiN x thin films for surface passivation of HgCdTe epitaxial layers. The hydrogenated amorphous SiN x films under study were deposited by a SENTECH SI500D inductively coupled plasma-enhanced chemical vapor deposition (ICPECVD) system with a high-density and low-ion-energy plasma source at relatively low substrate temperatures (80°C to 100°C). A series of SiN x films were first deposited on CdTe/GaAs and Si substrates under different deposition conditions to examine the influence of ICP power, deposition temperature, and NH3/SiH4 ratio on properties of the SiN x films. To investigate SiN x deposition conditions suitable for surface passivation of HgCdTe, the SiN x /n-Hg0.68Cd0.32Te interface characteristics were investigated employing capacitance–voltage measurements, and the corresponding interface trap densities D it were extracted from the high-frequency and low-frequency characteristics. Analysis of SiN x /n-Hg0.68Cd0.32Te metal–insulator–semiconductor (MIS) structures indicated that Si-rich SiN x films deposited at 100°C by ICPECVD exhibit electrical characteristics suitable for surface passivation of HgCdTe-based devices, that is, interface trap densities in the range of mid-1010 cm−2 eV−1 and fixed negative interface charge densities of ∼1011 cm−2. In addition, the relationship between bond concentration and surface passivation performance has been explored based on infrared (IR) absorbance spectra. The Si–H and N–H bond concentrations were found to be directly correlated with passivation performance, such that SiN x films with a combination of high [Si–H] and low [N–H] bond concentrations were found to be suitable as electrical passivation layers on HgCdTe.
    No preview · Article · Mar 2015 · Journal of Electronic Materials
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    ABSTRACT: In this paper, we present a theoretical study of mercury cadmium telluride (HgCdTe)-based unipolar n-type/barrier/n-type (nBn) infrared (IR) detector structures for midwave IR and longwave IR spectral bands. To achieve the ultimate performance of nBn detectors, a bandgap engineering method is proposed to remove the undesirable valence band discontinuity that is currently limiting the performance of conventional HgCdTe nBn detectors. Our proposed band engineering method relies on simultaneous grading of the barrier composition and doping density profiles, leading to efficient elimination of the valence band discontinuity. This allows the detector to operate at |V-bias| < 50 mV, rendering all tunneling-related dark current components insignificant and allowing the detector to achieve the maximum possible diffusion current limited performance.
    Full-text · Article · Mar 2015 · IEEE Transactions on Electron Devices
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    ABSTRACT: The nanomechanical movements of microcantilevers are a unique tool for the detection of various chemicals. When a microcantilever is functionalized with a surface which specifically adsorbs the chemical of interest, the resulting surface stress will bend the microcantilever. The measurement of this bending can provide an accurate measure of the concentration of the chemical of interest. Here we consider the use of microcantilevers to detect hydrogen under ambient atmospheric conditions. We find that nanomechanical movements of a palladium/silicon nitride cantilever tip correspond to sub-milliTorr changes in the partial pressure of hydrogen in air.
    No preview · Article · Feb 2015

Publication Stats

3k Citations
470.04 Total Impact Points

Institutions

  • 1900-2015
    • University of Western Australia
      • • School of Electrical, Electronic and Computer Engineering
      • • Microelectronics Research Group (MRG)
      Perth City, Western Australia, Australia
  • 2004
    • University of California, Santa Barbara
      • Department of Electrical and Computer Engineering
      Santa Barbara, California, United States
  • 1999
    • Korea Advanced Institute of Science and Technology
      • Department of Electrical Engineering
      Daiden, Daejeon, South Korea
  • 1982
    • Lehigh University
      Bethlehem, Pennsylvania, United States