Impact of GaN cap on charges in Al2O3/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations
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作者:
Tapajna, M.
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Slovak Acad Sci, Inst Elect Engn, Bratislava 84104, SlovakiaSlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Tapajna, M.
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Jurkovic, M.
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Slovak Acad Sci, Inst Elect Engn, Bratislava 84104, SlovakiaSlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Jurkovic, M.
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Valik, L.
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Slovak Acad Sci, Inst Elect Engn, Bratislava 84104, SlovakiaSlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Valik, L.
[1
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Hascik, S.
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Slovak Acad Sci, Inst Elect Engn, Bratislava 84104, SlovakiaSlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Hascik, S.
[1
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Gregusova, D.
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Slovak Acad Sci, Inst Elect Engn, Bratislava 84104, SlovakiaSlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Gregusova, D.
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Brunner, F.
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Ferdinand Braun Inst, Leibniz Inst Hochstfrequenztech, D-12489 Berlin, GermanySlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Brunner, F.
[2
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Cho, E. -M.
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Ferdinand Braun Inst, Leibniz Inst Hochstfrequenztech, D-12489 Berlin, GermanySlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Cho, E. -M.
[2
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Hashizume, T.
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Hokkaido Univ, RCIQE, Sapporo, Hokkaido 0600814, Japan
JST CREST, Tokyo 1020075, JapanSlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Hashizume, T.
[3
,4
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Kuzmik, J.
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Slovak Acad Sci, Inst Elect Engn, Bratislava 84104, SlovakiaSlovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
Kuzmik, J.
[1
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机构:
[1] Slovak Acad Sci, Inst Elect Engn, Bratislava 84104, Slovakia
[2] Ferdinand Braun Inst, Leibniz Inst Hochstfrequenztech, D-12489 Berlin, Germany
[3] Hokkaido Univ, RCIQE, Sapporo, Hokkaido 0600814, Japan
Oxide/semiconductor interface trap density (D-it) and net charge of Al2O3/(GaN)/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with and without GaN cap were comparatively analyzed using comprehensive capacitance measurements and simulations. D-it distribution was determined in full band gap of the barrier using combination of three complementary capacitance techniques. A remarkably higher D-it (similar to 5-8 X 10(12) eV(-1) cm(-2)) was found at trap energies ranging from E-C-0.5 to 1 eV for structure with GaN cap compared to that (D-it similar to 2-3 X 10(12) eV(-1) cm(-2)) where the GaN cap was selectively etched away. D-it distributions were then used for simulation of capacitance-voltage characteristics. A good agreement between experimental and simulated capacitance-voltage characteristics affected by interface traps suggests (i) that very high D-it (>10(13) eV(-1) cm(-2)) close to the barrier conduction band edge hampers accumulation of free electron in the barrier layer and (ii) the higher D-it centered about E-C-0.6 eV can solely account for the increased C-V hysteresis observed for MOS-HEMT structure with GaN cap. Analysis of the threshold voltage dependence on Al2O3 thickness for both MOS-HEMT structures suggests that (i) positive charge, which compensates the surface polarization, is not necessarily formed during the growth of III-N heterostructure, and (ii) its density is similar to the total surface polarization charge of the GaN/AlGaN barrier, rather than surface polarization of the top GaN layer only. Some constraints for the positive surface compensating charge are discussed. (C) 2014 AIP Publishing LLC.