Ron=0.33 Ω•mmが得られた。
以上より、非極性m面AlGaN/GaN構造を用いる事で、Vth=+2 V、かつ、
Ron=0.33 Ω•mmのノーマリオフ型AlGaN/GaN FETが設計された。
図3.9 Proposed recessed-gate MIS structure of enhancement-mode m-plane AlGaN/GaN FETs.
GaN AlGaN
S G D
Delta-doped layer Gate dielectric
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図3.10 A band diagram and carrier profile of recessed-MIS structure m-plane AlGaN/GaN FETs.
-4 -3 -2 -1 0 1 2 3 4 5
0 00
0 100100100100 200200200 300200 300300 400300 400400400 500500500500 600600600 700600 700700700
Energy (eV)
Distance [ÅÅÅÅ]
0.00E+00 2.00E+17 4.00E+17 6.00E+17 8.00E+17 1.00E+18
0 100 200 300 400 500 600 700
Electron concentration [cm-3]
Distance (ÅÅÅÅ) m-plane GaN m-plane
AlGaN Al2O3
Distance (ÅÅÅÅ) 1.0
0.8 0.6 0.4 0.2 0 [××××1018]
n(cm-3)
(Å)
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3.5 結言 結言 結言 結言
本章では、ノーマリオフ型AlGaN/GaN FET実現のため、極性c面
AlGaN/GaN構造に対する、非極性m面AlGaN/GaN構造の優位性を示した。ま
た、m面AlGaN/GaN構造を用いたノーマリオフ型AlGaN/GaN FETの設計につ
いて述べた。
●分極効果の無い非極性m面AlGaN/GaN構造を用いる事で、極性c面 AlGaN/GaN構造より、
9 高いVthが得られる事を計算により示した。
●m面GaN中においても、c面GaNと同等のバンド構造、µ、φBの物性値を有 する事が示された。
●m面AlGaN中へドナー不純物を導入する事で、m面AlGaN/GaN界面へ2DEG
を生成する事ができ、m面AlGaN/GaN FETのアクセス領域作製が可能である事 が示された。
●m面AlGaN中へ不純物をδドーピングする事で、nparを低く抑えつつ均一ドー
ピング時より高いns = 6.1×1012 cm-2が得られる事が示された。
●リセスMIS構造m面AlGaN/GaN FETにおいて、Vth=+2 VかつRon=0.33 Ω•mm のノーマリオフ型AlGaN/GaN FETが設計された。
以上より、m面AlGaN/GaN構造を用いて、高Vthかつ低Ronを有するノ ーマリオフ型AlGaN/GaN FETが設計された。
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