Publications

Results 51–75 of 283
Skip to search filters

High Temperature and Power Dependent Photoluminescence Analysis on Commercial Lighting and Display LED Materials for Future Power Electronic Modules

Scientific Reports

Sabbar, Abbas; Madhusoodhanan, Syam; Al-Kabi, Sattar; Dong, Binzhong; Wang, Jiangbo; Atcitty, Stanley A.; Kaplar, Robert K.; Ding, Ding; Mantooth, Alan; Yu, Shui Q.; Chen, Zhong

Commercial light emitting diode (LED) materials - blue (i.e., InGaN/GaN multiple quantum wells (MQWs) for display and lighting), green (i.e., InGaN/GaN MQWs for display), and red (i.e., Al0.05Ga0.45In0.5P/Al0.4Ga0.1In0.5P for display) are evaluated in range of temperature (77–800) K for future applications in high density power electronic modules. The spontaneous emission quantum efficiency (QE) of blue, green, and red LED materials with different wavelengths was calculated using photoluminescence (PL) spectroscopy. The spontaneous emission QE was obtained based on a known model so-called the ABC model. This model has been recently used extensively to calculate the internal quantum efficiency and its droop in the III-nitride LED. At 800 K, the spontaneous emission quantum efficiencies are around 40% for blue for lighting and blue for display LED materials, and it is about 44.5% for green for display LED materials. The spontaneous emission QE is approximately 30% for red for display LED material at 800 K. The advance reported in this paper evidences the possibility of improving high temperature optocouplers with an operating temperature of 500 K and above.

More Details
TYPE Journal Article YEAR 2019
ScopusOSTIDOI

Bevel edge termination for vertical GaN power diodes

2019 IEEE 7th Workshop on Wide Bandgap Power Devices and Applications, WiPDA 2019

Binder, Andrew B.; Dickerson, Jeramy R.; Crawford, Mary H.; Pickrell, Gregory P.; Allerman, A.A.; Sharps, Paul; Kaplar, Robert K.

Edge termination for vertical power devices presents a significant challenge, as improper termination can result in devices with a breakdown voltage significantly less than the ideal infinite-planar case. Edge termination for vertical GaN devices is particularly challenging due to limitations in ion implantation for GaN, and as such this work investigates a bevel edge termination technique that does not require implantation and has proven to be effective for Si and SiC power devices. However, due to key differences between GaN versus Si and SiC p-n junctions (specifically, a grown versus an implanted junction), this technology needs to be reevaluated for GaN. Simulation results suggest that by leveraging the effective bevel angle relationship, a 10-15° physical bevel angle can yield devices with 85-90% of the ideal breakdown voltage. Results are presented for a negative bevel edge termination on an ideally 2 kV vertical GaN p-n diode.

More Details
TYPE Conference Poster YEAR 2019
ScopusOSTIDOI

Saturation Velocity Measurement of Al0.7Ga0.3N-Channel High Electron Mobility Transistors

Journal of Electronic Materials

Klein, Brianna A.; Baca, A.G.; Lepkowski, Stefan M.; Nordquist, Christopher N.; Wendt, J.R.; Allerman, A.A.; Armstrong, Andrew A.; Douglas, Erica A.; Abate, Vincent M.; Kaplar, Robert K.

Gate length dependent (80 nm–5000 mm) radio frequency measurements to extract saturation velocity are reported for Al0.85Ga0.15N/Al0.7Ga0.3N high electron mobility transistors fabricated into radio frequency devices using electron beam lithography. Direct current characterization revealed the threshold voltage shifting positively with increasing gate length, with devices changing from depletion mode to enhancement mode when the gate length was greater than or equal to 450 nm. Transconductance varied from 10 mS/mm to 25 mS/mm, with the 450 nm device having the highest values. Maximum drain current density was 268 mA/mm at 10 V gate bias. Scattering-parameter characterization revealed a maximum unity gain bandwidth (fT) of 28 GHz, achieved by the 80 nm gate length device. A saturation velocity value of 3.8 × 106 cm/s, or 35% of the maximum saturation velocity reported for GaN, was extracted from the fT measurements.

More Details
TYPE Journal Article YEAR 2019
ScopusOSTIDOI

Stability in Fluorine-Treated Al-Rich High Electron Mobility Transistors with 85% Al-Barrier Composition

IEEE International Reliability Physics Symposium Proceedings

Baca, A.G.; Klein, B.A.; Armstrong, Andrew A.; Allerman, A.A.; Douglas, Erica A.; Fortune, Torben R.; Kaplar, Robert K.

Combined with recess etching, Al-rich III-N high electron mobility transistors (HEMTs) can be treated with a reactive ion etch plasma to implant F- ions into the HEMT's near surface region for a positive threshold voltage $(V-{TH})$ shift to achieve enhancement-mode (e-mode) operation. These HEMTs, along with depletion-mode (d-mode) controls that lack fluorine treatment, were evaluated for F- ion stability using step-stress and fixed-bias stress experiments. Step-stress experiments identified parametric shifts as a function of the drain-voltage $(V-{DS})$ stress prior to catastrophic failure that occurred at ${\it V-{DS}}$ ranging between 70-75 V. Fixed bias stressing at $V-{DS}=50\mathrm{V}$ was conducted at $190\ ^{\circ}\mathrm{C}$ Both e- and d- mode HEMTs exhibited a negative $V-{TH}$ shift of $0.6-1.0 \mathrm{V}$ during early time stressing at 190°C, with minor on-resistance effects, but both HEMT types were thereafter stable up to 4 hours. The early time changes are common to both e-mode and d-mode HEMTs and the F-induced ${\it V-{TH}}$ delta between e- and d-mode HEMTs remains intact within the bias-temperature stressing conditions of this work.

More Details
TYPE Conference Poster YEAR 2019
ScopusOSTIDOI
Results 51–75 of 283
Results 51–75 of 283