Prof. Fei Gao Profile

Prof. Fei Gao

Professor at Univ of Michigan

SPIE Involvement:

Author

Proceedings Article | 2 March 2020 Presentation + Paper

Role of point-defect charging dynamics in quantum-well magneto-transport

Danhong Huang, Andrii Iurov, Godfrey Gumbs, Fei Gao

Proceedings Volume 11274, 112740A (2020) https://doi.org/10.1117/12.2540028

KEYWORDS: Electrons, Quantum wells, Dielectric polarization, Scattering, Dielectrics, Thermodynamics, Chemical species, Semiconductors, Phonons, Radiation effects

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Proceedings Article | 18 September 2018 Presentation + Paper

Microscopic theory for point-defect effects on photon absorption in quantum-well systems

D. Huang, A. Iurov, F. Gao, G. Gumbs, D. Cardimona

Proceedings Volume 10766, 1076603 (2018) https://doi.org/10.1117/12.2318562

KEYWORDS: Electrons, Absorption, Quantum wells, Chemical species, Scattering, Polarization, Tolerancing, Dielectric polarization, Plasmons, Photodetectors

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Proceedings Article | 18 September 2018 Presentation + Paper

Atomic-level based non-ionizing energy loss: an application to GaAs and GaN semiconductor materials

Fei Gao, Nanjun Chen, Danhong Huang, Eric Heller, Paul LeVan

Proceedings Volume 10766, 1076604 (2018) https://doi.org/10.1117/12.2324351

KEYWORDS: Gallium arsenide, Gallium nitride, Chemical species, Particles, Computer simulations, Semiconductors, Gallium, Picosecond phenomena, Xenon, Analytical research

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Large-scale molecular dynamics (MD) simulations, along with bond-order interatomic potentials, have been employed to study defect production, clustering and their evolution within high energy displacement cascades in semiconductors. Based on the MD results, the damage density within a cascade core is evaluated, and used to describe a new energy partition function. In addition, we have further developed a model to determine the non-ionizing energy loss (NIEL) for semiconductors, which can be used to predict the displacement damage degradation induced by space radiation on electronic components. The atomic-level based NIEL model has been applied to GaAs and GaN. At low energies, the most surviving defects are single interstitials and vacancies, and only 20% of the interstitial population is contained in clusters in GaAs, but a direct-impact amorphization in GaAs occurs with a high degree of probability during the cascade lifetime for Ga PKAs (primary knock-on atoms) with energies higher than 2 keV. However, a large number of atoms will be displaced during the collisional phase with a compacted cascade volume in GaN, and consequently, a great number of displaced atoms recombine significantly with vacancies at the same time, i.e., a pseudo-metallic behavior (PMB). This leads to the result that the majority of surviving defects are just single interstitials or vacancies for all recoil energies considered with only a small number of defects forming clusters. The total number of defects simulated in GaN can be very well predicted by the simplied Norgett, Robison and Torrens (NRT) formula due to the PMB, in contrast to GaAs where the defect number becomes much larger than the NRT value. The calculated NIEL in GaN is often found smaller than that predicted by a model based on the simple Kinchin-Pease formula. The comparisons of defect creation, density and effective NIEL in GaN to those of GaAs suggest that GaN may be much more resistant to displacement damage than GaAs, and therefore, very suitable for use in high-power space-energy systems and space-probe applications.

Proceedings Article | 1 September 2015 Paper

Microscopic model for studying radiation degradation of electron transport and photodetection devices

Danhong Huang, Fei Gao, D. Cardimona, C. Morath, V. Cowan

Proceedings Volume 9616, 96160S (2015) https://doi.org/10.1117/12.2186610

KEYWORDS: Chemical species, Instrument modeling, Particles, Sensors, Tolerancing, Crystals, Electron transport, Photodetectors, Ions, Electronic components

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Proceedings Article | 9 September 2014 Paper

Radiation response of inorganic scintillators: insights from Monte Carlo simulations

Micah Prange, Dangxin Wu, Yulong Xie, Luke Campbell, Fei Gao, Sebastien Kerisit

Proceedings Volume 9213, 92130L (2014) https://doi.org/10.1117/12.2063818

KEYWORDS: Acoustics, Data modeling, Monte Carlo methods, Picosecond phenomena, Scattering, Scintillators, Thermal modeling, Phonons, Particles, Electrons

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Proceedings Article | 26 September 2013 Paper

Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality

R. Williams, Joel Grim, Qi Li, K. Ucer, G. Bizarri, S. Kerisit, Fei Gao, P. Bhattacharya, E. Tupitsyn, E. Rowe, V. Buliga, A. Burger

Proceedings Volume 8852, 88520J (2013) https://doi.org/10.1117/12.2027716

KEYWORDS: Excitons, Diffusion, Scintillators, Quenching (fluorescence), Data modeling, Phonons, Picosecond phenomena, Monte Carlo methods, Absorption, Crystals

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Proceedings Article | 28 April 2011 Paper

On a novel self-regulating shape memory polymer composite

Fei Gao, Seyul Son, Kyungmook Park, David Biggs, Courtney Andrews, Eric Mockensturm, Nakhiah Goulbourne

Proceedings Volume 7978, 797816 (2011) https://doi.org/10.1117/12.881930

KEYWORDS: Silica, Capillaries, Composites, Glasses, Digital image correlation, Shape memory polymers, Polymers, Microelectromechanical systems, Neodymium, Polyurethane

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Polyurethane shape memory polymers (PU-SMPs) are active materials that can be transformed into complex shapes with the ability to recover their original shape even after undergoing large deformations. Because of their light weight, large recoverability, low cost, and high compliance, SMPs can be potentially employed as actuators, MEMS devices, temperature sensors, and damping elements to name a few. One of the key challenges in implementing SMPs is the response time which is limited by the method of heating and cooling and the material. Unlike shape memory alloys, SMPs can be activated by multiple stimuli including lasers, resistive heating, electric fields, and magnetic fields. While these methods may provide an efficient way of heating the SMP, they rely on the slow process of passive conduction for cooling. In this paper, a self regulating SMP (SR-SMP) composite is introduced, whereby a novel heating and cooling system consisting of embedded silica capillary tubes in the SMP (DiAPLEX® MP4510: SMP Technologies, Inc.) has been developed. The tubes are used to pump hot/cold fluid through the SMP membrane and hence provide a local temperature source. In order to show the effectiveness and efficiency of the mechanism, the thermomechanical response of the SR-SMP is compared experimentally to a SMP with "conventional" i.e. global heating and cooling mechanisms. It is shown that the SR-SMP has a faster thermomechanical response. It has been demonstrated previously that soft SMPs can be controlled by an electric field while in the rubbery phase, thus taking advantage of the Maxwell stress or electrostatic stress effect. Thermomechanical characterization of PU-SMPs is described for different weight percentages of resin (Diphenylmethane-4, 4'-diisocyanate) and hardener (1,4-Butanediol). Varying the percent hardener reduced the effective cross-link density of the polymer and hence the thermomechanical properties. The electromechanical response of pure SMP and SR-SMP is predicted numerically. The numerical computation indicates that the softer SMPs (resin:hardener = 5:4, 8:7, and 9:8) could be used as electroactive polymers.

Showing 5 of 7 publications

Conference Committee Involvement (7)

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XX

20 August 2018 | San Diego, California, United States

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XIX

7 August 2017 | San Diego, California, United States

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII

29 August 2016 | San Diego, California, United States

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVII

10 August 2015 | San Diego, California, United States

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVI

18 August 2014 | San Diego, California, United States

Showing 5 of 7 Conference Committees

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