A5007638548- Semiconductor Quantum Structures and Devices
- Advanced Semiconductor Detectors and Materials
- Chalcogenide Semiconductor Thin Films
- Semiconductor Lasers and Optical Devices
- ZnO doping and properties
- Quantum Dots Synthesis And Properties
- Photonic and Optical Devices
- Ferroelectric and Piezoelectric Materials
- Semiconductor materials and devices
- Acoustic Wave Resonator Technologies
- Nanowire Synthesis and Applications
- Spectroscopy and Laser Applications
- Optical Coatings and Gratings
- Energy Harvesting in Wireless Networks
- Ga2O3 and related materials
- solar cell performance optimization
- Photonic Crystals and Applications
- Electronic and Structural Properties of Oxides
- Infrared Target Detection Methodologies
- Neuroscience and Neural Engineering
- Thin-Film Transistor Technologies
- Advanced Memory and Neural Computing
- Innovative Energy Harvesting Technologies
- Quantum and electron transport phenomena
- Thermography and Photoacoustic Techniques
University of Delaware
2020-2025
Vancouver Coastal Health Research Institute
2018-2023
University of British Columbia
2018-2023
University of Michigan
2013-2022
Ann Arbor Center for Independent Living
2016-2022
Michigan United
1998-2020
Vancouver Coastal Health
2018
Universidad Politécnica de Madrid
2017
University of Illinois Urbana-Champaign
2014
University of California, Santa Barbara
2014
A narrow-band transmission filter is demonstrated near normal incidence that operates through relaxation of supported-mode selection rules and explained in the context group theory. We calculated transverse magnetic electric dispersion relations a dielectric grating subwavelength near-wavelength region using finite element modal analysis determine modes' corresponding irreducible representations. Coupling to select modes at optimized yield broadband high reflectance acts as background for...
Abstract Ambient energy harvesting has great potential to contribute sustainable development and address growing environmental challenges. Converting waste from energy-intensive processes systems (e.g. combustion engines furnaces) is crucial reducing their impact achieving net-zero emissions. Compact harvesters will also be key powering the exponentially smart devices ecosystem that part of Internet Things, thus enabling futuristic applications can improve our quality life homes, cities,...
The physical properties of detectors based on intraband optical absorption in quantum dots is described and examined the interest providing a competitive alternative infrared (IR) detector technology. These dot are an extension well photodetectors expected to have large performance advantage. A model developed for fundamental limitations enabling direct comparison between IR materials technologies. made among HgCdTe, well, detectors, where potential outperform wells by several orders...
We report far-infrared photoconductivity in self-organized InAs/GaAs quantum dots grown by molecular beam epitaxy. Through use of a Fourier transform infrared spectrometer, signal peaked at 17 μm is observed from n–i–n detector structure with doped InAs the intrinsic region. Comparison photoluminescence and band-to-band photocurrent absorption spectra suggests response due to intersubband transitions dots.
Oxygen doping in ZnTe is applied to a junction diode the aim of utilizing associated electron states 0.5 eV below bandedge as an intermediate band for photovoltaic solar cells. The ZnTe:O diodes confirm extended spectral response relative undoped diodes, and demonstrate 100% increase short circuit current, 15% decrease open voltage, overall 50% power conversion efficiency. Subbandgap excitation at 650 1550 nm confirms via two-photon process illustrates proposed energy mechanism cell.
We report the room-temperature operating characteristics of InGaAs/GaAs self-organised quantum dot lasers grown by molecular beam epitaxy. The emission wavelength is 1.028 µm and Jth = 650 A/cm2 for a 90 × 1 mm broad-area laser. Steady-state time-resolved photoluminescence measurements confirm that lasing occurs through e1-hh2 higher-order transition, spontaneous recombination time this transition ≃ 200 ps.
The use of self-assembled InAs-GaAs quantum dots in photoconductive intersubband detectors the far-infrared is presented. Far-infrared absorption observed 6-18-/spl mu/m range for subband-subband and subband-continuum transitions. Photoconductive quantum-dot were fabricated demonstrate tunable operating wavelengths between 6-18 /spl using or AlAs barriers allows further tuning to shorter 3-7 mu/m. Subband-continuum dot show encouraging normal incidence performance characteristics at T=40 K,...
A unipolar, barrier-integrated HgCdTe nBn photodetector with all n-type doping and a type-I band lineup is experimentally demonstrated. Planar mid-wave infrared (MWIR) devices exhibit current-voltage (I-V) characteristics that are consistent inversion in reverse bias, indicating barrier-influenced behavior. Dark current saturation observed beyond bias of approximately −0.8 V. Bias-dependent photoresponse the cut-off wavelength around 5.7 μm. Numerical modeling based on experimental results...
Indoor photovoltaic energy harvesting is a promising candidate to power millimeter (mm)-scale systems. The theoretical efficiency and electrical performance of photovoltaics under typical indoor lighting conditions are analyzed. Commercial crystalline Si fabricated GaAs Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> As cells were experimentally measured simulated AM 1.5 solar...
Quantum-dot infrared photodetectors (QDIPs) are being studied extensively for mid-wavelength and long-wavelength detection because they offer normal-incidence, high-temperature, multispectral operation. Intersubband absorption, carrier lifetime, gain parameters that need to be better characterized, understood, controlled in order realize high-performance QDIPs. An eight-band k/spl middot/p model is used calculate polarization-dependent intersubband absorption. The calculated trend absorption...
Photoconductivity is observed in ZnO epilayers due to photoexcitation the visible spectral region of 400-700 nm, below bandgap energy 3.4 eV.Photoconductive transients have time constants order minutes.Treatment surface with SiO 2 passivation layers results a significant reduction photoconductive signal and constant.The response attributed hole traps ZnO, where rate equation model presented describe characteristics.A method extracting trap density spectrum on basis assumptions for capture...
Intergrowth of two partially miscible phases BiFeO3 and BiMnO3 gives a new class room-temperature multiferroic phase, Bi3Fe2Mn2O10+δ, which has unique supercell (SC) structure. The SC heterostructures exhibit simultaneously ferrimagnetism remanent polarization. These results open up avenue for exploring single-phase thin films by controlling the phase mixing perovskite BiRO3 (R = Cr, Mn, Fe, Co, Ni) materials. As service to our authors readers, this journal provides supporting information...
Wireless biomedical implantable devices on the mm-scale enable a wide range of applications for human health, safety, and identification, though energy harvesting power generation are still looming challenges that impede their widespread application. Energy scavenging approaches to implants have included thermal [1-3], kinetic [4-6], radio-frequency [7-11] radiative sources [12-14]. However, achievement efficient at has been elusive. Here we show photovoltaic cells can achieve conversion...
The electrical characteristics of ZnO thin-film transistors with high-k (Ba,Sr)TiO3 gate dielectrics are presented. and thin films were deposited on Pt, exhibiting polycrystalline characteristics. devices demonstrated transistor behavior over the range 0–10V a stable threshold voltage approximately 1.2V. field effect mobility, subthreshold slope, on/off ratio measured to be 2.3cm2V−1s−1, 0.25V∕decade, 1.5×108, respectively. performance suggest that ZnO∕(Ba,Sr)TiO3 structures well suited for...
Self-organized growth of InGaAs/GaAs strained epitaxial layers gives rise to an ordered array islands via the Stranski-Krastanow mode, for misfits >1.8%. These are pyramidal in shape with a base diagonal /spl sim/20 nm and height sim/6-7 nm, depending parameters. They therefore exhibit electronic properties zero-dimensional systems, or quantum dots. One more such dots can be stacked vertically coupled form gain region lasers. We have investigated single-layer dot (SLQD) multilayer (MLQD)...
In this paper, a new application of ferroelectric thin film based on electrostrictive and piezoelectric effects is reported. Electrostrictive resonances in the can be controlled with DC electrical field. A switchable bulk wave acoustic resonator (FBAR) proposed using barium strontium titanate (BST) film. The measured has parallel resonance at 2.035 GHz series 1.975 25 V bias applied. electromechanical coupling coefficient was calculated to approximately 7.07% which comparable AIN FBARs....
A model for intermediate band solar cells is presented to assess the effect of carrier transport and recombination (CTR) on efficiency these devices. The includes dependencies physical parameters including optical absorption, lifetime, density electronic states. Simulation results using this indicate that conversion degrades when net lifetime small (range nanoseconds) or device length long relative drift length. cell provides a method determining realistic efficiencies based experimentally...
GaAs photovoltaics are promising candidates for indoor energy harvesting to power small-scale ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 1$ </tex-math></inline-formula> mm <sup xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) electronics. This application has stringent requirements on dark current, recombination, and shunt leakage paths due low-light conditions small device dimensions....
Brain machine interfaces using neural recording systems [1]–[4] can enable motor prediction [5]–[6] for accurate arm and hand control in paralyzed or severely injured individuals. However, implantable have historically used wires data communication power, increasing risks of tissue damage, infection, cerebrospinal fluid leakage, rendering these devices unsuitable long-term implantation (Fig. 26.9.1, top). Recently, several wireless miniaturized implants with various power transmission...
Abstract Memristors have emerged as transformative devices to enable neuromorphic and in‐memory computing, where success requires the identification development of materials that can overcome challenges in retention device variability. Here, high‐entropy oxide composed Zr, Hf, Nb, Ta, Mo, W oxides is first demonstrated a switching material for valence change memory. This multielement provides uniform distribution higher concentration oxygen vacancies, limiting stochastic behavior resistive...
Miniaturized and wireless near-infrared (NIR) based neural recorders with optical powering data telemetry have been introduced as a promising approach for safe long-term monitoring the smallest physical dimension among state-of-the-art standalone recorders. However, main challenge NIR recording ICs is to maintain robust operation in presence of light-induced parasitic short circuit current from junction diodes. This especially true when signal currents are kept small reduce power...
We report small-signal modulation bandwidth and differential gain measurements of a single-layer self-organized In0.4Ga0.6As/GaAs quantum dot laser grown by molecular beam epitaxy. The 3 dB single-mode ridge waveguide lasers was measured to be 7.5 GHz at 100 mA under pulsed measurements, demonstrating the possibility high speed operation these devices. 1.7×10−14 cm2.
We report far-infrared absorption in directly doped self-organized InAs quantum dots. Photoluminescence spectra demonstrate a blue shift peak intensity for increasing doping the Far-infrared measurements using Fourier transform infrared spectrometer show range of 13–18 μm dots with Al0.15Ga0.85As and GaAs as barrier material.