Dr. Anand V. Sampath Profile

Dr. Anand V. Sampath

at DEVCOM Army Research Lab

SPIE Involvement:

Author

Publications (16)

Proceedings Article | 15 June 2023 Presentation + Paper

Studies of spatial uniformity and jitter in SiC UV SPADs

Anand Sampath, Gregory Garrett, Jonathan Schuster, Jeremy Smith, Michael Derenge, Daniel Habersat, Brenda VanMil, Reza Gandhi, Sergei Dolinsky, Edwin Heilweil, Joshua Bienfang, Enrico Bellotti, Michael Wraback

Proceedings Volume 12512, 1251206 (2023) https://doi.org/10.1117/12.2663387

KEYWORDS: Silicon carbide, Single photon avalanche diodes, Avalanche photodetectors, Temporal resolution, Ultraviolet radiation

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Proceedings Article | 10 March 2023 Presentation + Paper

Design and optimization of NUV-enhanced 4H-SiC separate-absorption-charge-multiplication avalanche photodiodes

Jonathan Schuster, Anand Sampath, Jeremy Smith, Stephen Kelley, Gregory Garrett, Daniel Habersat, Michael Derenge, Michael Wraback, Dina Bower, Shahid Aslam, Tilak Hewagama

Proceedings Volume 12415, 1241509 (2023) https://doi.org/10.1117/12.2649236

KEYWORDS: Silicon carbide, Avalanche photodetectors, Doping, Absorption, Deep ultraviolet, Ultraviolet radiation, Avalanche photodiodes, Finite-difference time-domain method, Design and modelling, Ionization

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Proceedings Article | 12 September 2019 Presentation

Investigation of 4H-SiC UV-APDs in Geiger and linear mode operation (Conference Presentation)

Chelsea Haughn, Stephen Kelley, Jeremy Smith, Kimberley Olver, Eric DeCuir, Jerry Cabalo, Michael Wraback, Eugene Chong, Anand Sampath

Proceedings Volume 11126, 1112602 (2019) https://doi.org/10.1117/12.2530822

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Proceedings Article | 9 September 2019 Presentation + Paper

Development of nanostructured antireflection coatings for infrared sensing applications

Ashok Sood, John Zeller, Adam Sood, Gopal Pethuraja, Roger Welser, Harry Efstathiadis, Anand Sampath, Nibir Dhar

Proceedings Volume 11129, 111290I (2019) https://doi.org/10.1117/12.2531642

KEYWORDS: Antireflective coatings, Nanostructuring, Infrared detection, Infrared technology, Long wavelength infrared, Roads, Optical components, Ultraviolet radiation, Night vision, Infrared sensors

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Proceedings Article | 18 May 2017 Presentation + Paper

Photoelectrochemistry of III-V epitaxial layers and nanowires for solar energy conversion

Vijay Parameshwaran, Ryan Enck, Roy Chung, Stephen Kelley, Anand Sampath, Meredith Reed, Xiaoqing Xu, Bruce Clemens

Proceedings Volume 10194, 101940N (2017) https://doi.org/10.1117/12.2264950

KEYWORDS: Electrodes, Resistance, Group III-V semiconductors, Semiconductors, Polarization, Gallium nitride, Particles, Interfaces, P-type semiconductors, Indium gallium nitride, Solar energy, Photoelectrochemical processes, Nanowires, Chemical reactions, Silicon, Indium nitride, Absorption, Indium gallium phosphide

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Proceedings Article | 25 May 2012 Paper

III-V nitride semiconductors for solar hydrogen production

Vijay Parameshwaran, Chad Gallinat, Ryan Enck, Anand Sampath, Paul Shen, Tevye Kuykendall, Shaul Aloni, Michael Wraback, Bruce Clemens

Proceedings Volume 8377, 83770B (2012) https://doi.org/10.1117/12.925200

KEYWORDS: Semiconductors, Indium gallium nitride, Electrodes, Silicon, Gallium nitride, Photons, Gallium, Hydrogen, Absorption, Semiconductor materials

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Proceedings Article | 19 May 2012 Paper

III-nitride/SiC avalanche photodetectors for enabling compact biological agent identification and detection

A. Sampath, R. Enck, C. Gallinat, H. Shen, M. Wraback, Q. Zhou, D. McIntosh, J. Campbell

Proceedings Volume 8376, 83760O (2012) https://doi.org/10.1117/12.918866

KEYWORDS: Silicon carbide, Gallium nitride, Avalanche photodetectors, Absorption, Interfaces, Polarization, Sensors, Quantum efficiency, Aluminum nitride, Biological detection systems

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Proceedings Article | 8 February 2007 Paper

Enhanced luminescence from AlxGa1-xN/AlyGa1-yN quantum wells grown by gas source molecular beam epitaxy with ammonia

Sergey Nikishin, Boris Borisov, Gregory Garrett, Wendy Sarney, Anand Sampath, Hongen Shen, Michael Wraback, Mark Holtz

Proceedings Volume 6473, 647306 (2007) https://doi.org/10.1117/12.701394

KEYWORDS: Gallium, Aluminum, Quantum wells, Luminescence, Quantum dots, Aluminum nitride, Molecular beam epitaxy, Transmission electron microscopy, Light emitting diodes, Picosecond phenomena

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Proceedings Article | 2 February 2007 Paper

Optimization of nanoscale phenomena in AlGaN for improved UV emitters

M. Wraback, G. Garrett, A. Sampath, H. Shen

Proceedings Volume 6479, 64791H (2007) https://doi.org/10.1117/12.699181

KEYWORDS: Excitons, Picosecond phenomena, Luminescence, Ultraviolet radiation, Light emitting diodes, Internal quantum efficiency, Gallium nitride, Temperature metrology, Diffusion, Aluminum

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Proceedings Article | 13 October 2006 Paper

Device challenges for biodetection

M. Wraback, M. Reed, G. Garrett, A. Sampath, H. Shen

Proceedings Volume 6398, 63980W (2006) https://doi.org/10.1117/12.693124

KEYWORDS: Gallium nitride, Picosecond phenomena, Light emitting diodes, Luminescence, Avalanche photodetectors, Ultraviolet radiation, Semiconductors, Sensors, Ultraviolet light emitting diodes, Avalanche photodiodes

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Proceedings Article | 25 March 2005 Paper

Fundamental studies of nanoscale phenomena in ultraviolet photonic materials and devices

Michael Wraback, Gregory Garrett, Anand Sampath, Charles Collins, Sergey Rudin, H. Shen

Proceedings Volume 5732, (2005) https://doi.org/10.1117/12.588010

KEYWORDS: Picosecond phenomena, Aluminum, Gallium, Gallium nitride, Ultraviolet radiation, Electron transport, Sapphire, Light emitting diodes, Semiconductors, Luminescence

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Proceedings Article | 29 December 2004 Paper

AlGaN materials for semiconductor sensors and emitters in 200- to 365-nm range

Alexander Usikov, Elizaveta Shapvalova, Yuri Melnik, Vladimir Ivantsov, Vladimir Dmitriev, Charles Collins, Anand Sampath, Gregory Garrett, Paul Shen, Michael Wraback

Proceedings Volume 5617, (2004) https://doi.org/10.1117/12.578452

KEYWORDS: Gallium nitride, Aluminum nitride, Silicon carbide, Doping, Gallium, Sapphire, Magnesium, Zinc, Ultraviolet radiation, Silicon

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Proceedings Article | 29 December 2004 Paper

Make light, not heat: toward higher efficiency nitride semiconductor ultraviolet optical sources

Michael Wraback, Gregory Garrett, Anand Sampath, Charles Collins, Paul Shen

Proceedings Volume 5617, (2004) https://doi.org/10.1117/12.581202

KEYWORDS: Picosecond phenomena, Gallium nitride, Aluminum, Aluminum nitride, Luminescence, Indium, Gallium, Quantum wells, Semiconductors, Ultraviolet radiation

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We have used subpicosecond time-resolved photoluminescence (TRPL) downconversion techniques to study the interplay of carrier localization and radiative and nonradiative processes in the active regions of light emitting III-nitride semiconductor ultraviolet optical sources, with the goal of identifying potential approaches that will lead to higher radiative efficiency. Comparison of TRPL in (In)AlGaN multiple quantum well active regions indicate that for addition of only 0.01 In content the PL decay time in an InAlGaN MQW is more than double that in an AlGaN MQW designed to emit at the same wavelength (360 nm), thus indicating the importance of indium for improvement of material quality, most likely through the suppression of point defects. This result is further underscored by TRPL data on 320 nm InAlGaN MQW active regions, which exhibit longer PL lifetimes than expected for growth on GaN templates with dislocation densities in the mid-10⁸cm^-2 range. While the PL lifetimes in these InAlGaN MQWs improve for growth on lower dislocation density HVPE bulk GaN substrates, a similar phenomenon is not observed for deposition on nearly dislocation-free bulk AlN substrates, suggesting that defect generation in the MQWs associated with lattice mismatch or AlN surface preparation may play an important role. The pump intensity dependence of the time zero signal and the TRPL decays in the MQWs implies that internal electric field-induced recombination through the barriers and interface states plays an important role in the radiative efficiency of quantum well active regions for c-axis oriented materials and devices. The effect of these internal electric fields can be mitigated through the use of nonpolar MQWs. The combination of more intense time-integrated PL spectra and shorter PL lifetimes with decreasing well width in GaN/AlGaN MQWs grown on a-plane LEO GaN for low pump intensity suggests that the radiative lifetime becomes shorter due to the accompanying increase in exciton binding energy and oscillator strength at smaller well width in these high quality samples. Finally, it is demonstrated that compositional fluctuations in AlGaN active regions grown by plasma-assisted MBE can be employed to create spatial localization that enhances the luminescence efficiency and PL lifetime (300-400 ps) despite high defect density (>10¹⁰cm^-2) by inhibiting movement of carriers to nonradiative sites. Significant enhancement of this phenomenon has been obtained in a DH LED structure grown on a lower defect density (mid-10⁹cm^-2) AlGaN template, with PL lifetime increased by nearly a factor of two, corresponding to a defect density in the mid-10⁷ cm^-2 range, and only a 3.3 times drop in PL intensity when the temperature is raised from 12 K to room temperature, suggesting up to ~ 30% internal quantum efficiency.

Proceedings Article | 30 May 2003 Paper

Femtosecond optical studies of carrier localization and recombination in III-nitride semiconductors

Michael Wraback, G. Garrett, A. Sampath, C. Collins, Hongen Shen

Proceedings Volume 4992, (2003) https://doi.org/10.1117/12.475715

KEYWORDS: Gallium nitride, Aluminum, Picosecond phenomena, Reflectivity, Luminescence, Semiconductors, Gallium, Sapphire, Ultrafast phenomena, Absorption

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We have used femtosecond time-resolved reflectivity and luminescence downconversion techniques to study carrier relaxation, localization, and recombination in III-nitride semiconductors. Intensity dependent, frequency degenerate pump-probe reflectivity measurements employing near-bandgap excitation provide information about initial carrier localization, subsequent ultrafast heat generation due to nonradiative recombination or trapping in states deep in the bandgap, and photoinduced absorption associated with excitation of carriers from localized states to the bands. These phenomena and their experimental signatures are illustrated for Al_0.25Ga_0.75N and Al_0.4Ga_0.6N samples, in which the photoinduced change in reflectivity ΔR decays faster with decreasing intensity and changes sign, with faster decays for a given intensity in the higher Al content sample. This behavior suggests that in these cases the dynamics are governed by trapping at localized states associated with alloy fluctuations that become deeper and more numerous as the Al content increases. Within this context the sign change and subsequent temporal evolution of ΔR may be indicative of ultrafast heat generation and/or photoinduced absorption, depending upon A1 content. Nondegenerate pump-probe reflectivity experiments designed to separate the electronic contributions of the ΔR decays from the slower thermal components by using a sub-bandgap probe are used to measure carrier lifetime in GaN. Comparison with data obtained from frequency degenerate experiment sunder identical excitation conditions employing a near bandgap probe indicate that in the frequency degenerate case the decay times in ΔR are inflated due to the presence of an additional long-lived component with the same sign as the electronic contribution. The sign and power dependence of this slow decay suggest that it may be associated with screening of a surface electric field by carriers trapped in deep states. In addition, a new technique is presented that employs luminescence downconversion using an ultrashort gating pulse to enable the characterization of UV light emission from III-nitride semiconductors with subpicosecond temporal resolution. This technique also allows one to measure PL rise times and fast components of multiple decays in the subsequent time evolution of the PL intensity. Comparison of luminescence emission intensity and lifetime in GaN and AlGaN with ~0.1 Al content grown homoepitaxially on GaN templates with the same quantities measured in heteroepitaxial layers grown on sapphire indicate significant improvement in the homoepitaxial layers due to reduction in defect density. Fast (<15 ps) initial decays in the AlGaN are attributed to localization in shallow traps associated with alloy fluctuations, with subsequent recombination through gap states.

Proceedings Article | 13 April 2000 Paper

GaN Schottky diode ultraviolet detectors grown by molecular beam epitaxy

Mira Misra, Anand Sampath, E. Iliopoulos, Theodore Moustakas

Proceedings Volume 3948, (2000) https://doi.org/10.1117/12.382135

KEYWORDS: Diodes, Gallium nitride, Sensors, Photodiodes, Reactive ion etching, Metals, Etching, Doping, Ultraviolet radiation, Molecular beam epitaxy

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Proceedings Article | 13 April 2000 Paper

GaN photodiodes grown by MBE on HVPE and ELO-HVPE GaN\sapphire substrates

Anand Sampath, E. Iliopoulos, K. Seth, Y. Fedyunin, Mira Misra, HockMin Ng, Phil Lamarre, Ze'ev Feit, Theodore Moustakas

Proceedings Volume 3948, (2000) https://doi.org/10.1117/12.382132

KEYWORDS: Gallium nitride, Diodes, Sapphire, Error control coding, Photodiodes, Nickel, Epitaxial lateral overgrowth, Gold, Visible radiation, Absorption

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Showing 5 of 16 publications

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