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On-Chip Optical-coupled Quantum Hall Devices in THz range

Oct 4 2006/ Seminar Department of Physics / NTHU. On-Chip Optical-coupled Quantum Hall Devices in THz range. Jeng-Chung Chen. Outline. The study of Single-electron transistor Device characterization Excited electronic states in closed QD Discussion Conclusion

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On-Chip Optical-coupled Quantum Hall Devices in THz range

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  1. Oct 4 2006/ Seminar Department of Physics / NTHU On-Chip Optical-coupled Quantum Hall Devices in THz range Jeng-Chung Chen

  2. Outline • The study of Single-electron transistor • Device characterization • Excited electronic states in closed QD • Discussion • Conclusion • On-chip optical-coupled QH devices • Passive THz scanning microscopes • Emitter: Hot spots • Detector QH detector • Device design • Future perspective

  3. Introduction: Technological and biological length scales

  4. Single Electron Transistor - Introduction SEM picture 100nm Lateral Confinement Technique Capacitive Charging Model Shadow Evaporation Technique Eg. diameter ~ 0.5-0.2m Cg ~100-10 aF C ~2-0.9 fF Al

  5. Device Characterization Lithographic size of QD : 570nm560nm Temperature: 70-100mK (a)

  6. Meta-stable states of QD observed by Al-SET

  7. Qualitative Discussion F0 V1=-1.18V

  8. Discussion: Emperical Model V1=-1.18V fixed In closed QD, regime 2-6

  9. Quantitative discussion U1 U2 UQD Cc~58.8aF, C1sg2=3.12aF

  10. Conclusion – First part • Kinetics of charging and discharging of closed quantum dots (QD)in a GaAs/AlGaAs heterostructure crystal are studied by anAluminum single electron transistor (Al-SET) electrostaticallycoupled to the quantum dot. • The period and conductance of CB peaksof Al-SET associated with different gating conditions revealseveral distinct regimes, strongly depending on the tunnelingbarriers of QD. • A lift-up and an uncovered sinking electronexcited state with long life time are realized in the completelyclosed dot. • An empirical model is proposed to explain the physicalorigins of these transitions. Ref: J.C. Chen, et al. Phys. Rev. B, 74, 045321 (2006).

  11. optics electronics THz microwaves visible x-ray g -ray MF, HF, VHF, UHF, SHF, EHF 0.3–30THz Hz 100 103 106 109 1015 1018 1021 1024 1012 kilo mega giga tera peta exa zetta yotta • 1 THz ~ 1 ps ~ 300 µm ~ 33 cm-1 ~ 4.1 meV Molecular vibration/rotation, Energy levels of quantum structures, magnetic resonance, collective excitations, transit times in mesoscopic devices, superconductor gaps… Biology, chemistry, medics, physics, astronomy, homeland security, environmental monitoring, non-destructive industrial testing, agriculture, …

  12. Picometrix Skin cancer TeraView Detection of chemical drugs Non-destructive check of IC Many applications extensivelydiscussed &studied Mapping of pharmaceutical tablets Security Airport control Medical diagnostics Science (2002)

  13. THz Imaging and Sensing Identification/characterization of the objects Conventional approach Object THz detection External light source THz, NIR, Visible Scattered, Reflected Transmitted P = nW-W Example: Daniel M. Mittleman et. al. IEEE Journal of Selected Topics in Quantum Electronics, 2, 679 (1996).

  14. THz Imaging and Sensing Our approach : Passive / noninvasive Object • Specific dynamics • of the object ? • Activity in • natural state ? THz Detection emitted P = 0.01fW-pW Example: Hall-bar emitter Temp: 4.2K, =2, I=100A, CE: 100pW Ref: K. Ikushima et al., Phys. Rev. Lett. 93, 146804(2004)

  15. μS - - - - -　 - μS N=3 - + S D N=2 μD μD + + + + + + N=1 U(r) U(r) ● B Δ μSD > ħωc /2 +ΔSD/2 S ΔU(r) D -ΔSD/2 Emitter: Hot spots in IQHE GaAs / AlGaAs heterostructure ħc = 10 meV Classical equi-potential lines in QH states • Higher LLs are fed with electrons via tunneling. Ref: Y.Kawano et al., Phys. Rev. B, 59, p.12537(1999)

  16. k= 2 cm-1 400μm 400 μm Detectors f =13 THz, ε= 10 meV, λ = 100μm, k = 100 cm-1 Detectors Sensitivity (NEP) Speed Narrowband Tunability Quantum Hall (QH)10-15 W/Hz1/2 1ms (Cyclotron resonance, GaAs/AlGaAs 2DEG) Y.Kawano et al., JAP, 89, 4037 (2001) H. Sakuma et al., Far-infrared Phys. & Technol., (2006) Kawano et.al., J. Appl. Phys 89 4037(2001)

  17. On-chip otical coupled quantum Hall devices Ohmic contacts Device design Temp: ~4.2K B_field: ~6-7T Optical consideration 2DEG Light propagation Absorption issue

  18. Study subjects Reference: Ref. C. Wood et al. Appl. Phys. Lett. 88,142103(2006) Organic polymer: benzocyclobutene (BCB) 4mm 1. Application: On-chip THz wave propagation (wave-guide design / switching rate) 2. Physics: (1) Onset of CE in IQHE (2) Temperature dependence (3) FQHE ??

  19. Biological activities Bio-molecules Bio-cell H.Fujitani et al.,J. Chem. Phys.  (2005) • Cell thermometry • Molecular “fingerprint” emission activated by ATP hydrolysis Electron dynamics in semiconductors & metals • Landau levels • Size quantization • (QD, 2D-subband) • Impurity levels • Superconductor  -gaps • etc.

  20. Future studies Limitation: low temperature ! e.g. QPC in high magnetic field Molecular CNT….etc. Objects Wave guide / antenna design THz photon detector Narrow band /Tunability e.g. Hall bar detector QD / Al-SET detector SIS detectors or mixers CNT….etc.

  21. Lowest: QD Highest: QHm Detected: Pdetect = 0.01aW  0.1pW Emission only from the focal point (10%) Efficiency of optical system (5%) Quantum efficiency of detector (5%) Total emitted: Ptotal CE = 100 aW 100 pW Energy conversion efficiency: 10-7 Electrical: P= RI 2= 3 nW 5 mW I = 500nA  400 μA Detector 10-4 - + e- 10-7 QH device I Intensity of CE

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