Publications

Results 226–250 of 304

Search results

Jump to search filters

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

Applied Physics Letters

Ihlefeld, Jon I.; Brumbach, Michael T.; Atcitty, Stanley A.

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.

More Details
TYPE Journal Article YEAR 2013
DOIOSTIScopus

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

ECS Transactions

Atcitty, Stanley A.; Kaplar, Robert K.; DasGupta, Sandeepan D.; Marinella, Matthew J.; 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.

More Details
TYPE Conference YEAR 2013
OSTIScopus

Impact of the Al mole fraction in the bulk- and surface-state induced instability of AlGaN/GaN HEMTs

Materials Research Society Symposium Proceedings

DasGupta, S.; Sun, M.; Armstrong, Andrew A.; Kaplar, Robert K.; Marinella, M.; Stanley, James B.; Smith, Mark A.; Atcitty, Stanley A.; Palacios, T.

Charge trapping and slow (10 s to > 1000 s) detrapping in AlGaN/GaN HEMTs designed for high breakdown voltage (> 1500 V) are studied to identify the impact of Al molefraction and passivation on trapping. Two different trapping components, TG1 (E a = 0.62 eV) and TG2 (with negligible temperature dependence) in AlGaN dominate under gale bias stress in the off-state. Al 0.15Ga 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 illumination by monochromatic light shows TD to have E a ≈ 1.65 eV in Al 0.26Ga 0.74N and E a ≈ 1.85 eV in Al 0.15Ga 0.85N. This is consistent with a transition from a deep state (E c - 2.0 eV) in the AlGaN barrier to the 2DEG. © 2012 Materials Research Society.

More Details
TYPE Conference YEAR 2012
ScopusOSTI

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 K.; Marinella, Matthew J.; Stanley, James B.; Atcitty, Stanley A.; 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.

More Details
TYPE Journal Article YEAR 2012
ScopusOSTIDOI
Results 226–250 of 304
Results 226–250 of 304