13 results on '"Blair C. Connelly"'
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2. Optical Field Induced Upconversion in Quantum Dots from Mid- and Long-Wavelength Infrared Radiation
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Keith A. Nelson, Ibrahim Boulares, Blair C. Connelly, and Jiaojian Shi
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Materials science ,business.industry ,Infrared ,Physics::Optics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,02 engineering and technology ,Optical field ,021001 nanoscience & nanotechnology ,01 natural sciences ,Photon upconversion ,010309 optics ,Quantum dot ,Electric field ,0103 physical sciences ,Optoelectronics ,Photonics ,0210 nano-technology ,business ,Absorption (electromagnetic radiation) ,Luminescence ,Astrophysics::Galaxy Astrophysics - Abstract
We investigate the interaction of the optical electric field of intense sub-picosecond infrared pulses, between 3.5 and 12 micrometers, with visible quantum dots materials. Significant visible luminescence is observed from upconversion of the infrared light. more...
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- 2020
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3. Dependence of minority carrier lifetime of Be-doped InAs/InAsSb type-II infrared superlattices on temperature and doping density
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Shin Mou, William C. Mitchel, Grace D. Metcalfe, H. E. Smith, Said Elhamri, Gail J. Brown, Michael Wraback, Elizabeth H. Steenbergen, and Blair C. Connelly
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010302 applied physics ,Materials science ,Photoluminescence ,Condensed matter physics ,Dopant ,Infrared ,business.industry ,Superlattice ,Doping ,technology, industry, and agriculture ,02 engineering and technology ,Carrier lifetime ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Residual carrier ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,0103 physical sciences ,Optoelectronics ,0210 nano-technology ,business ,Order of magnitude - Abstract
We investigate the minority carrier lifetime of Be-doped InAs/InAsSb type-II superlattices as a function of doping density and temperature using time-resolved photoluminescence (TRPL) to determine if switching the superlattice type from the typical n-type residual carrier concentration to p-type may improve device performance by improving the lifetime–mobility product. The introduction of the Be dopant to the superlattice reduces the carrier lifetime, first by a factor of ∼3 for doping densities near or below the n-type residual carrier concentration, then by an order of magnitude for samples doped well above the residual carrier concentration. Further, the higher-doped p-type samples demonstrate two distinct TRPL decay regimes and two peaks in the PL spectra, suggesting the formation of an additional acceptor-related recombination pathway leading to the observed shorter carrier lifetime. more...
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- 2015
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4. Investigation of Trap States in Mid-Wavelength Infrared Type II Superlattices Using Time-Resolved Photoluminescence
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Jill A. Nolde, Joseph S. Melinger, Michael Wraback, Edward H. Aifer, Blair C. Connelly, Chaffra A. Affouda, Eric M. Jackson, Chadwick L. Canedy, Jerry R. Meyer, Igor Vurgaftman, Hongen Shen, and Grace D. Metcalfe more...
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Photoluminescence ,Condensed matter physics ,Solid-state physics ,Infrared ,Chemistry ,Superlattice ,Fermi level ,Carrier lifetime ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Wavelength ,symbols.namesake ,Materials Chemistry ,symbols ,Electrical and Electronic Engineering ,Atomic physics ,Spectroscopy - Abstract
Time-resolved photoluminescence (TRPL) spectroscopy is used to study the minority-carrier lifetime in mid-wavelength infrared, n-type, InAs/Ga1−xInxSb type II superlattices (T2SLs) and investigate the recombination mechanisms and trap states that currently limit their performance. Observation of multiple exponential decays in the intensity-dependent TRPL data indicates trap saturation due to the filling then emptying of trap states and different Shockley–Read–Hall (SRH) lifetimes for minority and majority carriers, with τmaj (τn0) ≫ τmin (τp0). Simulation of the photoluminescence transient captures the qualitative behavior of the TRPL data as a function of temperature and excess carrier density. A trap state native to Ga1−xInxSb is identified from the low-injection temperature-dependent TRPL data and found to be located below the intrinsic Fermi level of the superlattice, approximately 60 ± 15 meV above the valence-band maximum. Low-temperature TRPL data show a variation of the minority-carrier SRH lifetime, τp0, over a set of InAs/Ga1−xInxSb T2SLs, where τp0 increases as x is varied from 0.04 to 0.065 and the relative layer thickness of Ga1−xInxSb is increased by 31%. more...
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- 2013
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5. TIME-RESOLVED PHOTOLUMINESCENCE STUDY OF TYPE II SUPERLATTICE STRUCTURES WITH VARYING ABSORBER WIDTHS
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Michael Wraback, Grace D. Metcalfe, Blair C. Connelly, and Paul H. Shen
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Photoluminescence ,Materials science ,Infrared ,business.industry ,Superlattice ,Carrier lifetime ,Molecular physics ,Acceptor ,Electronic, Optical and Magnetic Materials ,Hardware and Architecture ,Optoelectronics ,Spontaneous emission ,Electrical and Electronic Engineering ,business ,Excitation ,Recombination - Abstract
We report time-resolved photoluminescence measurements on a set of long-wave infrared InAs / GaSb type II superlattice absorber samples with various widths as a function of temperature and excitation density. Careful analysis of the photoluminescence data determines the minority carrier lifetime and background carrier density as a function of temperature, and provides information on the acceptor energy and density in each sample. Results indicate that carrier lifetime is dominated by Shockley-Read-Hall recombination with a lifetime of ~30 ns at 77 K for all samples. Below 40 K, background carriers are observed to freeze-out in conjunction with increased contributions from radiative recombination. An acceptor energy level of ~20 meV above the valance band is also determined for all samples. Variations of carrier lifetime between each sample do not strongly correlate with absorber width, indicating that barrier recombination is not the dominant factor limiting the carrier lifetime in our samples. more...
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- 2011
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6. Time-resolved photoluminescence study of carrier recombination and transport in type-II superlattice infrared detector materials
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Blair C. Connelly, Hongen Shen, Michael Wraback, and Grace D. Metcalfe
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chemistry.chemical_compound ,Gallium antimonide ,Photoluminescence ,Materials science ,chemistry ,Electron capture ,Superlattice ,Spontaneous emission ,Carrier lifetime ,Infrared detector ,Atomic physics ,Indium arsenide - Abstract
Time-resolved photoluminescence (TRPL) is used to study the minority carrier lifetime in type-II superlattice (T2SL) infrared detector materials to investigate the recombination mechanisms, trap states and transport properties that currently limit their performance. Measurements of carrier lifetime have shown that InAs/Ga1-xInxSb T2SLs are dominated by non-radiative Shockley-Read-Hall (SRH) recombination, resulting in short minority carrier lifetimes (10’s of nanoseconds at 77 K). A trap energy of ~60 meV above the valence band is identified in mid-wavelength infrared n-type InAs/Ga1-xInxSb T2SLs, where trap saturation (non-exponential decay) is observed under high injection levels due to a significantly faster hole capture rate than electron capture rate. Lifetime measurements in “Ga-free” InAs/InAs1-xSbx T2SLs exhibit an order-of-magnitude increase in lifetime (100’s of nanoseconds at 77 K) with contributions from both radiative and non-radiative recombination. This improvement is attributed to the reduction of non-radiative recombination centers from the superlattice with the elimination of Ga and suggests that the SRH trap(s) limiting the carrier lifetime of InAs/Ga1-xInxSb T2SLs is native to the Ga1-xInxSb layer. Additionally, radiative recombination is observed in an InAs/GaSb T2SL using a sub-bandgap CW laser to saturate the SRH recombination centers, yielding a radiative lifetime of ~140 ns at 77 K. Since carrier transport is a concern in Ga-free T2SLs, it is investigated by studying samples grown with and without barriers (to contain injected carriers to the absorber region). It is determined that carrier transport is poor in InAs/InAs1-xSbx T2SLs because negligible differences are observed in the carrier lifetime. more...
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- 2013
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7. Study of Temperature-Dependent Carrier Transport in a p-GaN/i-InGaN/n-GaN Solar Cell Heterostructure using Ultrafast Spectroscopy
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Grace D. Metcalfe, Samantha C. Cruz, Steven P. DenBaars, Robert M. Farrell, Hongen Shen, Anand V. Sampath, Meredith Reed, Carl J. Neufeld, Yutaka Terao, Michael Iza, Naresh C. Das, Shuji Nakamura, Michael Wraback, Lee E. Rodak, Jordan R. Lang, Nathan G. Young, James S. Speck, Stacia Keller, Nathaniel T. Woodward, Blair C. Connelly, and Umesh K. Mishra more...
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Materials science ,business.industry ,Gallium nitride ,Heterojunction ,Polarization (waves) ,Photon counting ,Quantitative Biology::Cell Behavior ,law.invention ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,law ,Electric field ,Solar cell ,Optoelectronics ,Physics::Chemical Physics ,business ,Spectroscopy ,Ultrashort pulse - Abstract
Temperature-dependent carrier transport is investigated using ultrafast spectroscopy in a p-GaN/i-InGaN/n-GaN solar cell with heavily-doped layers to compensate for polarization charges at the hetero-interface. We observe a flip in the transport direction at 110 K. more...
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- 2013
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8. Temperature-dependent minority carrier lifetimes of InAs/InAs1-xSbxtype-II superlattices
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Oray Orkun Cellek, Elizabeth H. Steenbergen, Blair C. Connelly, Michael Wraback, Grace D. Metcalfe, Said Elhamri, A. W. K. Liu, Dmitri Lubyshev, Hongen Shen, Yong-Hang Zhang, Joel M. Fastenau, and Yueming Qiu more...
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Physics ,chemistry.chemical_compound ,Photoluminescence ,Condensed matter physics ,chemistry ,Infrared ,Superlattice ,Spontaneous emission ,Quantum efficiency ,Carrier lifetime ,Indium arsenide ,Atomic physics ,Dark current - Abstract
Temperature-dependent minority carrier lifetimes of InAs/InAs1-xSbx type-II superlattices are presented. The longest lifetime at 11 K is 504 ± 40 ns and at 77 K is 412 ± 25 ns. Samples with long periods and small wave function overlaps have both non-radiative and radiative recombination mechanisms apparent, with comparable contributions from both near 77 K, and radiative recombination dominating at low temperatures. Samples with short periods and large wave function overlaps have radiative recombination dominating from 10 K until ~200 K. The improved lifetimes observed will enable long minority carrier lifetime superlattices to be designed for high quantum efficiency, low dark current infrared detectors. more...
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- 2012
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9. Polarization Enhanced Carrier Transport in a p-down n-GaN/i-InGaN/p-GaN Solar Cell Structure
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Shuai Zhou, Kenneth A. Jones, Grace D. Metcalfe, Blair C. Connelly, Randy P. Tompkins, Chad S. Gallinat, Ryan Enck, Michael Wraback, Nathaniel T. Woodward, and Paul H. Shen
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Materials science ,business.industry ,Photovoltaic system ,Wide-bandgap semiconductor ,Polarization (waves) ,Terahertz spectroscopy and technology ,law.invention ,Optical pumping ,Solar cell efficiency ,law ,Electric field ,Solar cell ,Optoelectronics ,business - Abstract
Evidence of a strong electric field aiding carrier collection is observed in an n-GaN/i-InGaN/p-GaN inverted polarity solar cell structure, detected by pump-probe electroabsorption and THz spectroscopy. more...
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- 2012
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10. Study of recombination mechanisms limiting the performance of Sb-based III-V type II superlattices for infrared detectors
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Michael Wraback, Hongen Shen, Blair C. Connelly, and Grace D. Metcalfe
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Physics ,Photoluminescence ,business.industry ,Band gap ,Superlattice ,Doping ,Carrier lifetime ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Acceptor ,Condensed Matter::Materials Science ,Optoelectronics ,Exponential decay ,business ,Quantum well - Abstract
Time-resolved photoluminescence measurements are used to study minority carrier lifetimes in type II superlattices (T2- SL) to investigate the recombination mechanisms that currently limit their performance. Time-domain measurements of the photoluminescence signal demonstrate multiple exponential decay, which provide information on background carriers, acceptor states and trap states. The temperature dependence of the TRPL signal shows that the carrier lifetime is dominated by Shockley-Read-Hall recombination. Optimal sample design for photoluminescence measurements is discussed. Photoluminescence measurements and modeling of the time-resolved signal in device structures demonstrate that the restoring current in a narrow bandgap junction dominates the carrier recombination, leading to measured lifetimes that are ostensibly long. Experimental results are presented on T2-SL samples that vary the superlattice absorber width and doping level. The effect of the interface type on carrier lifetime is investigated in multiple quantum well structures. Variations of the absorber width, doping level and interface type are not found to strongly influence the carrier lifetime. more...
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- 2011
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11. Carrier lifetime studies in midwave infrared type-II InAs/GaSb strained layer superlattice
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Elena Plis, Blair C. Connelly, Thomas J. Rotter, Brianna Klein, Paul H. Shen, Grace D. Metcalfe, Sanjay Krishna, Ted Schuler-Sandy, Michael Wraback, and Nutan Gautam
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Materials science ,Photoluminescence ,Dopant ,Infrared ,business.industry ,Process Chemistry and Technology ,Superlattice ,Doping ,chemistry.chemical_element ,Carrier lifetime ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Materials Chemistry ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Tellurium ,Instrumentation ,Saturation (magnetic) - Abstract
The authors report on an investigation of the dependence of the minority carrier lifetime in midwave infrared InAs/GaSb strained layer superlattices on a number of varied parameters: layer placement of two dopants (either Be or Te), and interface treatment between InAs and GaSb layers. In samples where the dopant and doping location was varied, it was found that the nonintentionally doped control sample exhibited the longest lifetimes (∼49 ns at 77 K under low injection), followed by the Be-doped and the Te-doped samples. Regardless of the type of doping, samples with dopants in only the InAs layer appeared to have longer lifetimes [low injection: 15 ns (Be) more...
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- 2014
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12. Significantly improved minority carrier lifetime observed in a long-wavelength infrared III-V type-II superlattice comprised of InAs/InAsSb
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Dmitri Lubyshev, Oray Orkun Cellek, Grace D. Metcalfe, Elizabeth H. Steenbergen, Yueming Qiu, Said Elhamri, Michael Wraback, Joel M. Fastenau, Amy W. K. Liu, Blair C. Connelly, Hongen Shen, and Yong-Hang Zhang more...
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Long wavelength ,Photoluminescence ,Materials science ,Physics and Astronomy (miscellaneous) ,Infrared ,business.industry ,Superlattice ,Optoelectronics ,Photodetector ,Semiconductor superlattices ,Carrier lifetime ,business ,Excitation - Abstract
Time-resolved photoluminescence measurements reveal a minority carrier lifetime of >412 ns at 77 K under low excitation for a long-wavelength infrared InAs/InAs0.72Sb0.28 type-II superlattice (T2SL). This lifetime represents an order-of-magnitude increase in the minority carrier lifetime over previously reported lifetimes in long-wavelength infrared InAs/Ga1−xInxSb T2SLs. The considerably longer lifetime is attributed to a reduction of non-radiative recombination centers with the removal of Ga from the superlattice structure. This lifetime improvement may enable background limited T2SL long-wavelength infrared photodetectors at higher operating temperatures. more...
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- 2011
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13. Direct minority carrier lifetime measurements and recombination mechanisms in long-wave infrared type II superlattices using time-resolved photoluminescence
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Blair C. Connelly, Michael Wraback, Grace D. Metcalfe, and Hongen Shen
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symbols.namesake ,Photoluminescence ,Physics and Astronomy (miscellaneous) ,Auger effect ,Hall effect ,Chemistry ,Infrared ,symbols ,Spontaneous emission ,Carrier lifetime ,Atomic physics ,Acceptor ,Recombination - Abstract
We present a direct optical measurement of minority carrier lifetime as a function of temperature and excitation density in long-wave infrared InAs/GaSb type II superlattices using time-resolved photoluminescence. Results indicate that carrier lifetime is dominated by Shockley–Read–Hall recombination, with a lifetime of 30 ns at 77 K. Below 40 K, we observe a freeze-out of carriers and increased contributions from radiative recombination. High-injection measurements yield a radiative recombination coefficient of 1.8×10−10 cm3/s and an upper limit of the Auger recombination coefficient of 10−28 cm6/s at 60 K. An acceptor level of ∼20 meV above the valence band is also determined. more...
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- 2010
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