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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.

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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 D.; Armstrong, Andrew A.; Kaplar, Robert K.; Marinella, Matthew J.; Brock, Reinhard; Smith, Mark A.; Atcitty, Stanley A.

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 Conference YEAR 2012
ScopusOSTI

Final LDRD report : science-based solutions to achieve high-performance deep-UV laser diodes

Crawford, Mary H.; Allerman, A.A.; Armstrong, Andrew A.; Cross, Karen C.; Henry, Tania A.; Alessi, Leonard J.

We present the results of a three year LDRD project that has focused on overcoming major materials roadblocks to achieving AlGaN-based deep-UV laser diodes. We describe our growth approach to achieving AlGaN templates with greater than ten times reduction of threading dislocations which resulted in greater than seven times enhancement of AlGaN quantum well photoluminescence and 15 times increase in electroluminescence from LED test structures. We describe the application of deep-level optical spectroscopy to AlGaN epilayers to quantify deep level energies and densities and further correlate defect properties with AlGaN luminescence efficiency. We further review our development of p-type short period superlattice structures as an approach to mitigate the high acceptor activation energies in AlGaN alloys. Finally, we describe our laser diode fabrication process, highlighting the development of highly vertical and smooth etched laser facets, as well as characterization of resulting laser heterostructures.

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TYPE SAND Report YEAR 2011
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Sub-bandgap light-induced carrier generation at room temperature in 4H-SiC metal oxide semiconductor capacitors

Applied Physics Letters

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

Carrier generation characteristics in n-type substrate silicon carbide (SiC) metal oxide semiconductor capacitors induced by sub-bandgap energy light are reported. The generation rate is high enough to create an inversion layer in approximately 20 min with monochromatic front side illumination of energy 2.1 eV in 4H-SiC for electric fields less 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-C Si). © 2011 American Institute of Physics.

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TYPE Journal Article YEAR 2011
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Results 201–225 of 247
Results 201–225 of 247