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The Energy Frontier Research Center for Solid-State Lighting Science: Exploring New Materials Architectures and Light Emission Phenomena

Journal of Physical Chemistry C

Coltrin, Michael E.; Subramania, Ganapathi S.; Tsao, Jeffrey Y.; Wang, George T.; Wierer, Jonathan J.; Wright, Jeremy B.; Armstrong, Andrew A.; Brener, Igal; Chow, Weng W.; Crawford, Mary H.; Fischer, Arthur J.; Koleske, Daniel; Martin, James E.; Rohwer, Lauren E.S.

Abstract not provided.

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TYPE Journal Article YEAR 2014
OSTIDOI

Contribution of deep-level defects to decreasing radiative efficiency of InGaN/GaN quantum wells with increasing emission wavelength

Applied Physics Express

Armstrong, Andrew A.; Crawford, Mary H.; Koleske, Daniel

Deep-level optical spectroscopy (DLOS) and photoluminescence (PL) were used to understand the role of defects in reducing the internal quantum efficiency (IQE) of InxGa1-xN/GaN multiple quantum wells (MQWs) as the emission wavelength increased from approximately 450 to 530 nm, i.e., the "green gap". DLOS studies of light emitting diodes (LEDs) identified QW defects whose concentration increased significantly with increasing x. The effect of increased QW defect density on IQE was assessed by examining the PL of MQW samples. Green-emitting MQWs had lower IQE and required higher pump power to reach peak IQE, corroborating the important impact of enhanced non-radiative recombination at defects. © 2014 The Japan Society of Applied Physics.

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TYPE Journal Article YEAR 2014
OSTIScopus

GaN-based wide-bandgap power switching devices: From atoms to the grid

ECS Transactions

Atcitty, Stanley; Kaplar, Robert J.; Dasgupta, Sandeepan; Marinella, Matthew; Armstrong, Andrew A.; Biedermann, Laura B.; Smith, Mark A.

Emerging semiconductor switches based on the wide-bandgap semiconductor GaN have the potential to significantly improve the efficiency of portable power applications such as transportable energy storage. Such applications are likely to become more widespread as renewables such as wind and solar continue to come on-line. However, the long-term reliability of GaN-based power devices is relatively unexplored. In this paper, we describe joint work between Sandia National Laboratories and MIT on highvoltage AlGaN/GaN high electron mobility transistors. It is observed that the nature of current collapse is a strong function of bias conditions as well as device design, where factors such as Al composition in the barrier layer and surface passivation play a large role. Thermal and optical recovery experiments are performed to ascertain the nature of charge trapping in the device. Additionally, Kelvin-force microscopy measurements are used to evaluate the surface potential within the device. © The Electrochemical Society.

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TYPE Conference YEAR 2013
OSTIScopus

Slow detrapping transients due to gate and drain bias stress in high breakdown voltage AlGaN/GaN HEMTs

IEEE Transactions on Electron Devices

Dasgupta, Sandeepan; Sun, Min; Armstrong, Andrew A.; Kaplar, Robert J.; Marinella, Matthew; Stanley, James B.; Atcitty, Stanley; Palacios, Tomas

Charge trapping and slow (from 10 s to > 1000 s) detrapping in AlGaN/GaN high electron mobility transistors (HEMTs) designed for high breakdown voltages (> 1500 V) is studied through a combination of electrical, thermal, and optical methods to identify the impact of Al molefraction and passivation on trapping. Trapping due to 5-10 V drain bias stress in the on-state (V gs = 0) is found to have significantly slower recovery, compared with trapping in the off-state (V gs < V th, V ds = 0). Two different trapping components, i.e., TG1 (E a = 0.6 eV) and TG2 (with negligible temperature dependence), in AlGaN dominate under gate bias stress in the off-state. Al 0.15 Ga 0.85N shows much more vulnerability to trapping under gate stress in the absence of passivation than does AlGaN with a higher Al mole fraction. Under large drain bias, trapping is dominated by a much deeper trap TD. Detrapping under monochromatic light shows TD to have E a ≈ 1.65 eV. Carbon doping in the buffer is shown to introduce threshold voltage shifts, unlike any of the other traps. © 2012 IEEE.

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TYPE Journal Article YEAR 2012
ScopusOSTIDOI

Sub-bandgap light-induced carrier generation at room temperature in silicon carbide MOS capacitors

Materials Science Forum

Dasgupta, Sandeepan; Armstrong, Andrew A.; Kaplar, Robert J.; Marinella, Matthew; Smith, Mark A.; Atcitty, Stanley

Carrier generation characteristics in n-type substrate SiC MOS capacitors induced by sub-bandgap energy light are reported. The generation rate is high enough to create an inversion layer in ∼20 minutes with monochromatic light (front side illumination) of energy 2.1 eV (intensity ∼5×10 16 cm-2s-1) in 4H-SiC for electric fields smaller than 1 MV/cm. Generation and recovery results strongly indicate involvement of a metastable defect whose efficiency as a generation center increases under hole-rich and decreases under electron-rich conditions. The generation dependence on bias history and light energy shows the defect to have properties consistent with the metastable silicon vacancy / carbon vacancy-antisite complex (VSi/Vc-CSi). © (2012) Trans Tech Publications.

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TYPE Journal Article YEAR 2012
DOIOSTIScopus
Results 226–250 of 286
Results 226–250 of 286
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