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Localized hole on Carbon acceptors in an n-type doped quantum wire.

’05 11/29 For Akiyama Group members. Localized hole on Carbon acceptors in an n-type doped quantum wire. Toshiyuki Ihara. 11/29 this second version (latest) 11/25 first version. Motivation. これまでのドープ細線の場合. Carbon Acceptor をドープした場合. Hawrylak et al. Solid State Commun. 81, 525 (1992)

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Localized hole on Carbon acceptors in an n-type doped quantum wire.

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  1. ’05 11/29 For Akiyama Group members Localized hole on Carbon acceptors in an n-type doped quantum wire. Toshiyuki Ihara 11/29 this second version (latest) 11/25 first version

  2. Motivation これまでのドープ細線の場合 Carbon Acceptorをドープした場合 Hawrylak et al. Solid State Commun. 81, 525 (1992)    (1次元ドープ系の発光スペクトル理論計算) 破線:正孔が自由に動く場合(Band端が強い) 実線:正孔がアクセプタに局在した場合(FES効果でFermi端が強い) 発光スペクトルにFES効果が強く現れるに違いない。 あわよくば吸収スペクトルにも変化があるかも。

  3. Sample structure of an n-type doped quantum wire with carbon acceptor doping

  4. Photograph of sample

  5. I-V feature

  6. Ref. PL and PLE overview Eprb = 1.57eV (wire probe) Pex = 10mW T = 5K Vg = 0V - stem excitation PL and wire probe PLE I chose Arm Continuum onset (1.6eV) as Eex to measure PL spectra (in following pages)

  7. PL Vg dependence Eex = 1.6eV(Arm Continuum ex.) Pex = 10mW T=5K Ref. Akiyama et al. Solid State Commun. 122, 169 (2002) Wire region Additional Emission peaks are observed !!

  8. Arm Acceptor peak Eex = 1.6eV(Arm Continuum ex.) Pex = 10mW T=5K I changed the sample position to measure “Arm region” without wire. Arm region One of the additional Emission peaks is assigned as “Arm Acceptor” which comes from C-Acceptor state in Arm region !!

  9. Wire Acceptor peak Eex = 1.6eV(Arm Continuum ex.) Pex = 3mW T=5K At the low excitation power, A clear “Wire Acceptor” emission peak appears !! Wire region Wire Acceptor emission peak is observed clearly at low excitation power. (Acceptor peak shows saturation with increasing excitation power !?)

  10. PL ~ excitation power dependence Eex = 1.6eV(Arm Continuum ex.) Vg=0V T=5K PL spectra normalized by Wire Exciton peak intensity Intensity of Acceptor PL peaks show saturation with increasing excitation power.

  11. Energy gap between Exciton state and Acceptor state Armの方がExciton – Acceptorのエネルギー差が大きい。何を意味するか考え中。

  12. Arm Acceptor Resonant PLE Eprb = 1.563eV (Arm Acceptor probe) Pex = 10mW T = 5K In Acceptor system, both PL and PLE peak show blue shift with increasing electron density

  13. Wire Acceptor Resonant PLE

  14. PL scan Eex = 1.6eV(Arm Continuum ex.) Pex = 10mW T=5K 中励起(10mW) There are still ML fluctuations

  15. PL scan (low excitation power) Eex = 1.6eV(Arm Continuum ex.) Pex = 3mW T=5K 弱励起(3mW) 長時間露光 There are still ML fluctuations (and C-dope density fluctuation !?) .

  16. Conclusion Carbon Acceptor準位の発光ピークがwire/Arm共に驚くほどきれいに現れた。 Arm Acceptor のPLEがとりあえず測定できた。Wire AcceptorのPLEは難しそう。 特に注目すべき点 : Wire・Arm共に、Acceptorの発光ピークが電子濃度の増加と共にブルーシフトを示した (さらに、Arm Acceptorの吸収は発光ピークとほぼ同じエネルギー) このことは、Acceptor⇔Conduction bandの遷移でFES効果が強いことを表す。 WireでBand edgeの発光が消えるという事実は非常に重要。  ⇔ 一次元電子系の発光スペクトルの形状は、正孔の局在に非常に敏感である。 以前の論文(Akiyama et al. Solid State Commun. 122, 169 (2002))で報告した 「発光スペクトルの高エネルギー側の肩に現れるモコモコ」は、 一部の正孔が局在するために現れるFES効果と考えられる。

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