M. Z. Tidrow

RDECOM The United States Army, Абердин, Maryland, United States

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Publications (112)152.48 Total impact


  • No preview · Article · Jan 2016 · Applied Physics Letters
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    ABSTRACT: Minimization of operating bias and generation-recombination dark current in long wavelength infrared (LWIR) strained layer superlattice (SLS) detectors, consisting of a lightly doped p-type absorber layer and a wide band gap hole barrier, are investigated with respect to the band alignment between the wide band gap barrier and absorber layers. Dark current vs. bias, photoresponse, quantum efficiency, lifetime, and modeling are used to correlate device performance with the wide gap barrier composition. Decreases in dark current density and operating bias were observed as the conduction band of the wide gap barrier was lowered with respect to the absorber layer. The device achieved 95% of its maximum quantum efficiency at 0 V bias, and 100% by 0.05 V. This study demonstrates key device design parameters responsible for optimal performance of heterojunction based SLS LWIR detectors.
    No preview · Article · Nov 2014 · Infrared Physics & Technology
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    ABSTRACT: Focal plane arrays of strained layer superlattices (SLSs) composed of InAs/GaSb are excellent candidates for infrared imaging, but one key factor limiting their utility is the lack of a surface passivation technique capable of protecting the mesa sidewall from degradation. Along these lines, we demonstrate the use of aqueous 3-aminopropyl triethoxysilane (APTES) deposited as a surface functionalizing agent for subsequent polymer passivation on InAs and GaSb surfaces following a HCl/citric acid procedure to remove the conductive oxide In2O3. Using atomic force microscopy, variable angle spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and modeling with density functional theory (DFT), we demonstrate that APTES films can successfully be deposited on III-V substrates by spin coating and directly compare these films to those deposited on silicon substrates. The HCl/citric acid surface preparation treatment is particularly effective at removing In2O3 without the surface segregation of In oxides observed from use of HCl alone. However, HCl/citric acid surface treatment method does result in heavy oxidation of both Ga and Sb, accompanied by segregation of Ga oxide to the surface. Deposited APTES layer thickness did not depend on the substrate choice, and thicknesses between 1 and 20 nm were obtained for APTES solution concentrations ranging from 0.1 to 2.5 vol %. XPS results for the N1s band of APTES showed that the content of ionic nitrogen was high (∼50%) for the thinnest films (∼1 nm), and decreased with increasing film thickness. These results indicate that APTES can indeed be used to form a silane surface layer to cover III-V materials substrates. Such APTES silane layers may prove useful in surface passivation of these materials alone, or as surface functionalizing agents for subsequent covalent binding with polymer overlayers like polyimide.
    No preview · Article · Nov 2014 · Applied Surface Science
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    ABSTRACT: The efficacy of solution deposition of thiolated self-assembled monolayers (SAMs) has been explored for the purpose of passivating III-V type II superlattice (T2SL) photodetectors, more specifically a p-type heterojunction device. Sulfur passivation has previously been achieved on T2SL devices. However, degradation over time, temperature sensitivity and inconsistent reproducibility necessitate a physical encapsulate that can chemically bond to the chemical passivant. Thus, this research investigates two passivation methods, surface passivation with a thiol monolayer and passivation with a polymer encapsulant with a view toward future combination of these techniques. Analysis of the physical and chemical condition of the surface prior to deposition assisted in the development of ideal processes for optimized film quality. Successful deposition was facilitated by in situ oxide removal. Various commercially available functional (cysteamine) and non-functional (alkane) thiolated monolayers were investigated. Dark current was reduced by 3 orders of magnitude and achieved negligible surface leakage at low bias levels. The lowest dark current result, 7.69 × 10−6 A/cm2 at 50 mV, was achieved through passivation with cysteamine.
    No preview · Article · Nov 2014 · Infrared Physics & Technology
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    ABSTRACT: We report a DFT/GGA study of water adsorption and charge transfer at the relaxed (110) surfaces of several III–V binary semiconductors: GaAs, GaSb, and InAs. Our calculations are the first to show that adsorption of dissociated water changes the (110) surface structure. The characteristic III–V bond rotation through an angle of 30° is reversed. The buckled III–V bond at the semiconductor/water interface rotates into the surface through a new angle, which we calculate to be approximately 11° on all three binaries. Only dissociation of water – as opposed to chemisorption or physisorption – leads to this pseudo-unrelaxed configuration. We calculate geometries and reaction energies for several different adsorption mechanisms and find that molecular adsorption is the most favorable. We are able to reproduce binding configurations and energies for known adsorption sites on GaAs(110), but we also show new calculations for water on GaSb(110) and InAs(110). Lastly, we calculate the shift in electronic work function and induced surface dipole moment due to adsorbed water. We show that shifts in work function maximize at 1 ML of water, consistent with previous experimental works. Analysis of the partial charges and electron density reveals that adsorption of water polarizes the (110) surface, leading to local charge transfer across the semiconductor/water interface.
    No preview · Article · Apr 2014 · Surface Science
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    ABSTRACT: Design parameters for the heterojunction-based strained layer superlattice (SLS) long-wave infrared (LWIR) detector are investigated so that it operates at a lower bias voltage with lower dark current and higher photo response. At typical operating temperatures (T ∼ 77 K), the dark current of GaSb/InAs SLS LWIR detectors is dominated by the Shockley–Read–Hall (SRH) generation–recombination (g–r) process in the space-charge (depletion) region. In order to suppress this dark current, a wide bandgap region next to the absorber layer has been included in recent SLS designs. A series of heterojunction-based LWIR SLS detectors with various doping and barrier profiles have been designed and characterized. The significance of the doping profile and thickness of the wide-bandgap layer in optimization of the heterojunction-based SLS detector performance are exhibited from the modeling and experimental results of these devices.
    No preview · Article · Jul 2013 · Infrared Physics & Technology
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    ABSTRACT: Suppression of generation-recombination dark current and bias stability in long wavelength infrared (LWIR) strained layer superlattice (SLS) detectors, consisting of a lightly doped p-type absorber layer and a wide bandgap hole barrier, are investigated with respect to the wide bandgap barrier layer thickness and doping profile. Dark current IV, photoresponse, and theoretical modeling are used to correlate device performance with the widegap barrier design parameters. Decreased dark current density and increased operating bias were observed as the barrier thickness was increased. This study also identifies key device parameters responsible for optimal performance of heterojunction based SLS LWIR detector.
    No preview · Article · Jan 2013 · Applied Physics Letters
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    ABSTRACT: We report a type-II superlattice mid-wave infrared 320×256 imager at 81 K with the M-barrier design that achieved background limited performance (BLIP) and ∼99% operability. The 280 K blackbody's photon irradiance was limited by an aperture and a band-pass filter from 3.6 μm to 3.8 μm resulting in a total flux of ∼5×10(12) ph.cm(-2).s(-1). Under these low-light conditions, and consequently the use of a 13.5 ms integration time, the imager was observed to be BLIP thanks to a ∼5 pA dark current from the 27 μm wide pixels. The total noise was dominated by the photon flux and read-out circuit which gave the imager a noise equivalent input of ∼5×10(10) ph.cm(-2).s(-1) and temperature sensitivity of 9 mK with F/2.3 optics. Excellent imagery obtained using a 1-point correction alludes to the array's uniform responsivity.
    No preview · Article · Jun 2012 · Optics Letters
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    ABSTRACT: We present the results of the radiometric characterization of an ``M'' structure long wavelength infrared Type-II strained layer superlattice (SLS) infrared focal plane array (IRFPA) developed by Northwestern University (NWU). The performance of the M-structure SLS IRFPA was radiometrically characterized as a function of photon irradiance, integration time, operating temperature, and detector bias. Its performance is described using standard figures of merit: responsivity, noise, and noise equivalent irradiance. Assuming background limited performance operation at higher irradiances, the detector quantum efficiency for the SLS detector array is approximately 57%. The detector dark density at 80 K is 142 μA/cm2, which represents a factor of seven reduction from previously measured devices.
    No preview · Article · Jun 2012 · Optical Engineering
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    ABSTRACT: Theoretical modeling and experimental evidence show that the dark currents of antimonide (Sb)-based Type-II Superlattice (T2SL) detectors sensitive to long-wavelength infrared (LWIR) radiation are limited by the minority carrier lifetimes associated with the Shockley Read-Hall (SRH) generation-recombination process. Despite the low minority carrier lifetimes, the present photodiode dark current performance is achieved by increasing the background doping density of the absorber layers to NA ~ 2×1016 cm-3. This paper will discuss the measured minority carrier lifetimes of T2SL LWIR detectors with various background doping densities. To make comparisons, we designed several T2SL absorber layers sensitive in the LWIR range and p-type doped up to various densities. We find the minority carrier lifetimes are dominated by the SRH generation-recombination process. By analyzing minority carrier lifetime data as a function of excess carrier densities, we estimate SRH lifetimes and actual ionized acceptor densities of the absorber layers. The data are compared with the measured impurity doping densities of the detectors. In addition, we predict the type of flaws responsible for the SRH recombination process and narrow down the flaw energy level relative to the Fermi energy.
    No preview · Article · Jun 2011 · Optical Engineering
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    ABSTRACT: This paper will discuss the desired quantum efficiency and dark current density of type-II strained-layer superlattice detectors (T2SLS), and required read-noise levels for long-wavelength infrared (LWIR) imaging applications at various background levels. The computation begins with noise equivalent irradiance NEI requirements with the focal plane array (FPA) operating at near-background limited infrared photodetection (BLIP) performance conditions. The paper will theoretically analyze the quantum efficiency and the dark current based on various components such as: diffusion, generation–recombination and tunneling, and dependence on the minority carrier lifetime of T2SL detector material. These calculations show appropriate minority carrier lifetime of the detector material for the various flux levels discussed in the article.
    No preview · Article · May 2011 · Infrared Physics & Technology
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    ABSTRACT: Much progress has been made in the past 2 years in developing III-V antimonide-based superlattice infrared detectors and focal plane arrays (FPAs). In the area of detector material growth by molecular beam epitaxy, the wafer foundry group, helped by government-trusted entities and other partnering institutions, has leapfrogged many years of R&D effort to become the premier detector wafer supplier. The wafers produced are of high quality as measured by surface morphology, defect density, photoluminescence property, high-resolution X-ray diffraction, and diode current-voltage characteristics. In the area of detector design and FPA processing, the team-consisting of members from government laboratories, academia, and the FPA industry-has made rapid progress in device structure design, detector array etching, passivation, hybridization, and packaging. The progress is reflected in the steady reduction in FPA median darkcurrent density and improvement in median quantum efficiency, as well as reasonably low median noise-equivalent different temperature under 300 K scene background, when compared with the performance from some of the commercially available HgCdTe FPAs. In parallel with the FPA research and development effort, a small amount of funding has been devoted to measuring minority carrier lifetimes and to understanding life-killing defects and mechanisms of superlattice devices. Results of direct time-resolved photoluminescence measurement on superlattice absorbers indicate relatively short lifetimes (on the order of 30 ns) due to Shockley-Read-Hall mechanism. Modeling and curve fitting with diode current-voltage data indicate longer minority carrier lifetimes, although the best fit lifetime values differ greatly, possibly due to the difference in material quality and device structure. Several models or hypotheses have been proposed to explain experimental data. More data are required to validate these models and hypotheses. Further work is also necessary to reconcile the substantially different results from different groups and to truly understand the physics of minority carrier lifetimes, which is necessary to improve the lifetime and realize the theoretical promise of superlattice materials.
    No preview · Article · May 2011 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: The antimonide superlattice infrared detector technology program was established to explore new infrared detector materials and technology. The ultimate goal is to enhance the infrared sensor system capability and meet challenging requirements for many applications. Certain applications require large-format focal plane arrays (FPAs) for a wide field of view. These FPAs must be able to detect infrared signatures at long wavelengths, at low infrared background radiation, and with minimal spatial cross talk. Other applications require medium-format pixel, co-registered, dual-band capability with minimal spectral cross talk. Under the technology program, three leading research groups have focused on device architecture design, high-quality material growth and characterization, detector and detector array processing, hybridization, testing, and modeling. Tremendous progress has been made in the past few years. This is reflected in orders-of-magnitude reduction in detector dark-current density and substantial increase in quantum efficiency, as well as the demonstration of good-quality long-wavelength infrared FPAs. Many technical challenges must be overcome to realize the theoretical promise of superlattice infrared materials. These include further reduction in dark current density, growth of optically thick materials for high quantum efficiency, and elimination of FPA processing-related performance degradation. In addition, challenges in long-term research and development cost, superlattice material availability, FPA chip assembly availability, and industry sustainability are also to be met. A new program was established in 2009 with a scope that is different from the existing technology program. Called Fabrication of Superlattice Infrared FPA (FastFPA), this 4-year program sets its goal to establish U.S. industry capability of producing high-quality superlattice wafers and fabricating advanced FPAs. It uses horizontal integration strategy by leveraging existing III-V industry resources and taking advantage of years of valuable experiences amassed by the HgCdTe FPA industry. By end of the program span, three sets of FPAs will be demonstrated-a small-format long-wave FPA, a large-format long-wave FPA, and a medium-format dual-band FPA at long-wave and mid-wave infrared.
    No preview · Article · Apr 2010 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: Quantum well infrared photodetectors (QWIPs) are well known for their stability, high pixel-pixel uniformity and high pixel operability which are quintessential parameters for large area imaging arrays. In this paper we report the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP focal plane array (FPA). The dual-band QWIP device was developed by stacking two multi-quantum-well stacks tuned to absorb two different infrared wavelengths. The full width at half maximum (FWHM) of the midwave infrared (MWIR) band extends from 4.4-5.1 ¿m and FWHM of the long-wave infrared (LWIR) band extends from 7.8-8.8 ¿m. Dual-band QWIP detector arrays were hybridized with direct injection 30 ¿m pixel pitch megapixel dual-band simultaneously readable CMOS read out integrated circuits using the indium bump hybridization technique. The initial dual-band megapixel QWIP FPAs were cooled to 68 K operating temperature. The preliminary data taken from the first megapixel QWIP FPA has shown system NE¿T of 27 and 40 mK for MWIR and LWIR bands, respectively.
    No preview · Article · Mar 2010 · IEEE Journal of Quantum Electronics
  • Lucy Zheng · Meimei Tidrow
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    ABSTRACT: The performance of infrared focal plane arrays (IRFPAs) is usually described by a set of figures of merit and operating parameters. They include FPA format, pixel pitch, operating temperature, cut-on and cutoff wavelengths, median detectivity, uniformity, and integration time. This article examines the promise of superlattice infrared materials and how the improved FPA figure of merit affects sensor system performance as measured by range, update rate, size, power, and cost. A simple analysis shows that for space-based surveillance, the system cost, as measured by the number of hosting satellites, may be decreased substantially by using detector arrays with large array size and longer detection range. It also shows that to make long-wavelength superlattice IRFPAs useful for future space applications, the residual nonuniformity must be improved.
    No preview · Article · Nov 2009 · Infrared Physics & Technology
  • Meimei Z. Tidrow
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    ABSTRACT: Type II strained layer superlattice (SLS) has been making tremendous progress in the past few years funded by the Missile Defense Agency Advanced Technology Directorate (MDA/DV) under the Passive EO/IR Program. SLS has shown great potential as a future solution for infrared military systems. In this presentation, the most recent progress in SLS development will be presented. The presentation will also discuss the comparison of SLS with mercury–cadmium–telluride (HgCdTe) using Rule 07, SLS minority carrier lifetime issues, and future directions.
    No preview · Article · Nov 2009 · Infrared Physics & Technology
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    ABSTRACT: This paper reports the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band quantum well infrared photodetector (QWIP) focal plane array (FPA). The dual-band QWIP device was developed by stacking two multi-quantum-well stacks tuned to absorb two different infrared wavelengths. The full width at half maximum (FWHM) of the mid-wave infrared (MWIR) band extends from 4.4 to 5.1 μm and the FWHM of a long-wave infrared (LWIR) band extends from 7.8 to 8.8 μm. Dual-band QWIP detector arrays were hybridized with custom fabricated direct injection read out integrated circuits (ROICs) using the indium bump hybridization technique. The initial dual-band megapixel QWIP FPAs were cooled to 70 K operating temperature. The preliminary data taken from the first megapixel QWIP FPA has shown system NEΔT of 27 and 40 mK for MWIR and LWIR bands, respectively.
    No preview · Article · Nov 2009 · Infrared Physics & Technology
  • Source
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    ABSTRACT: Jet Propulsion Laboratory is actively developing the III-V based infrared detector and focal plane arrays (FPAs) for NASA, DoD, and commercial applications. Currently, we are working on multi-band Quantum Well Infrared Photodetectors (QWIPs), Superlattice detectors, and Quantum Dot Infrared Photodetector (QDIPs) technologies suitable for high pixel-pixel uniformity and high pixel operability large area imaging arrays. In this paper we report the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP focal plane array (FPA). In addition, we will present the latest advances in QDIPs and Superlattice infrared detectors at the Jet Propulsion Laboratory.
    Preview · Article · Aug 2009 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: In recent years, Type-II InAs/GaSb superlattice photodetectors have experienced significant improvements in material quality, structural designs, and imaging applications. They now appear to be a possible alternative to the state-of-the-art HgCdTe (MCT) technology in the long (LWIR) and very long wavelength infrared regimes. At the Center for Quantum Devices, we have successfully realized very high quantum efficiency, very high dynamic differential resistance R<sub>0</sub>A-product LWIR Type-II InAs/GaSb superlattice photodiodes with efficient surface passivation techniques. The demonstration of high-quality LWIR focal plane arrays that were 100% fabricated in-house reaffirms the pioneer position of this university-based laboratory.
    Preview · Article · Jul 2009 · Proceedings of the IEEE
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    ABSTRACT: We report the growth and characterization of type-II InAs/GaSb superlattice photodiodes grown on a GaAs substrate. Through a low nucleation temperature and a reduced growth rate, a smooth GaSb surface was obtained on the GaAs substrate with clear atomic steps and low roughness morphology. On the top of the GaSb buffer, a p+-i-n+ type-II InAs/GaSb superlattice photodiode was grown with a designed cutoff wavelength of 4 μm. The detector exhibited a differential resistance at zero bias (R0A) in excess of 1600 Ω cm2 and a quantum efficiency of 36.4% at 77 K, providing a specific detectivity of 6×1011 cm/W and a background limited operating temperature of 100 K with a 300 K background. Uncooled detectors showed similar performance to those grown on GaSb substrates with a carrier lifetime of 110 ns and a detectivity of 6×108 cm/W.
    No preview · Article · Jun 2009 · Applied Physics Letters

Publication Stats

2k Citations
152.48 Total Impact Points

Institutions

  • 2013-2014
    • RDECOM The United States Army
      Абердин, Maryland, United States
  • 1998-1999
    • Army Research Laboratory
      Aberdeen Proving Ground, Maryland, United States
    • University of Florida
      Gainesville, Florida, United States