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AlGaN composition dependence of the band offsets for epitaxial Gd2O3/AlxGa12xN (0 &lex &le0.67) heterostructures

Applied Physics Letters

Ihlefeld, Jon F.; Brumbach, Michael T.; Allerman, A.A.; Wheeler, David R.; Atcitty, Stanley

Gd2O3 films were prepared on (0001)-oriented AlxGa1-xN (0≤x≤0.67) thin film substrates via reactive molecular-beam epitaxy. X-ray diffraction revealed that these films possessed the cubic bixbyite structure regardless of substrate composition and were all 111-oriented with in-plane rotations to account for the symmetry difference between the oxide film and nitride epilayer. Valence band offsets were characterized by X-ray photoelectron spectroscopy and were determined to be 0.41±0.02eV, 0.17±0.02eV, and 0.06±0.03eV at the Gd2O3/AlxGa1-xN interfaces for x=0, 0.28, and 0.67, respectively.

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TYPE Journal Article YEAR 2014
DOIOSTIScopus

Trap-related parametric shifts under DC bias and switched operation life stress in power AlGaN/GaN HEMTs

IEEE International Reliability Physics Symposium Proceedings

Khalil, S.G.; Ray, L.; Chen, M.; Chu, R.; Zehnder, D.; Garrido, A.; Munsi, M.; Kim, S.; Hughes, B.; Boutros, K.; Kaplar, Robert; Dickerson, Jeramy; Dasgupta, S.; Atcitty, Stanley; Marinella, M.J.

This paper reports on trap-related shifts of the transfer curve and threshold voltage of power AlGaN/GaN HEMTs under switched bias operating life and reverse and forward DC bias stress. Opposite polarity threshold voltage shifts at room temperature under operating life and reverse bias stress conditions can be explained by means of drain current transient measurements under reverse bias stress conditions. A proposed model to explain the trapping/de-trapping behavior under different stress conditions is described and highlights the critical role of the electric field. Experimental evidence of the importance of the role of the electric field is seen in reduced parametric shift by improving the field plate design. © 2014 IEEE.

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TYPE Conference YEAR 2014
ScopusOSTI

Sensitivity analysis of a technique for the extraction of interface trap density in SiC MOSFETs from subthreshold characteristics

IEEE International Reliability Physics Symposium Proceedings

Hughart, David R.; Flicker, Jack D.; Atcitty, Stanley; Marinella, Matthew; Kaplar, Robert

A method for extracting interface trap density (DIT) from subthreshold I-V characteristics is used to analyze data on a SiC MOSFET stressed for thirty minutes at 175°C with a gate bias of-20 V. Without knowing the channel doping, the change in DIT can be calculated when referenced to an energy level correlated with the threshold voltage. © 2014 IEEE.

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TYPE Conference YEAR 2014
DOIOSTIScopus

Sensitivity analysis of a technique for the extraction of interface trap density in SiC MOSFETs from subthreshold characteristics

IEEE International Reliability Physics Symposium Proceedings

Hughart, David R.; Flicker, Jack D.; Atcitty, Stanley; Marinella, Matthew; Kaplar, Robert

A method for extracting interface trap density (DIT) from subthreshold I-V characteristics is used to analyze data on a SiC MOSFET stressed for thirty minutes at 175°C with a gate bias of-20 V. Without knowing the channel doping, the change in DIT can be calculated when referenced to an energy level correlated with the threshold voltage. © 2014 IEEE.

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TYPE Conference YEAR 2014
DOIOSTIScopus

Sensitivity analysis of a technique for the extraction of interface trap density in SiC MOSFETs from subthreshold characteristics

IEEE International Reliability Physics Symposium Proceedings

Hughart, David R.; Flicker, Jack D.; Atcitty, Stanley; Marinella, Matthew; Kaplar, Robert

A method for extracting interface trap density (DIT) from subthreshold I-V characteristics is used to analyze data on a SiC MOSFET stressed for thirty minutes at 175°C with a gate bias of-20 V. Without knowing the channel doping, the change in DIT can be calculated when referenced to an energy level correlated with the threshold voltage. © 2014 IEEE.

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TYPE Conference YEAR 2014
DOIOSTIScopus

Jemez Pueblo solar power study

43rd ASES National Solar Conference 2014, SOLAR 2014, Including the 39th National Passive Solar Conference and the 2nd Meeting of Young and Emerging Professionals in Renewable Energy

Acker, Thomas L.; John, Cherise; DeVore, Kaelyn; Tallas, Steven; Khatibi, Mehrdad; Vadiee, Nader; West, Jonathan; Collins, Matthew; Billie, Tomzak; Atcitty, Stanley

Northern Arizona University (NAU) and the Southwestern Indian Polytechnic Institute (SIPI) conducted a pre- feasibility study for utility-scale solar power on the Jemez Pueblo in New Mexico. Student groups at NAU and SIPI analyzed four different 40-MW solar power projects to understand whether or not such plants built on tribal lands are technically and financially feasible. The NREL System Advisor Model (SAM) was employed to analyze the following four alternatives: fixed, horizontal-axis photovoltaic (PV); fixed, tilted-at-latitude PV; horizontal, single-axis tracking PV; and a solar-thermal "power tower" plant. Under supervision from faculty, the student teams predicted the energy production and net present value for the four options. This paper presents details describing the solar power plants analyzed, the results of the SAM analyses, and a sensitivity analysis of the predicted performance to key input variables. Overall, solar power plants on the Jemez Pueblo lands appear to pass the test for financial feasibility.

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TYPE Conference YEAR 2014
ScopusOSTI

Band offsets of La2O3 on (0001) GaN grown by reactive molecular-beam epitaxy

Applied Physics Letters

Ihlefeld, Jon F.; Brumbach, Michael T.; Atcitty, Stanley

La2O3 films were prepared on (0001)-oriented GaN substrates via reactive molecular-beam epitaxy. Film orientation and phase were assessed using reflection high-energy electron and X-ray diffraction. Films were observed to grow as predominantly hexagonal La2O3 for thicknesses less than 10 nm while film thickness greater than 10 nm favored mixed cubic and hexagonal symmetries. Band offsets were characterized by X-ray photoelectron spectroscopy on hexagonally symmetric films and valence band offsets of 0.63 ± 0.04 eV at the La2O3/GaN interface were measured. A conduction band offset of approximately 1.5 eV could be inferred from the measured valence band offset. © 2013 AIP Publishing LLC.

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TYPE Journal Article YEAR 2013
DOIOSTIScopus

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

ECS Transactions

Atcitty, Stanley; Kaplar, Robert; 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
Results 201–250 of 306
Results 201–250 of 306