1 / 25

Infrared, Self Assembled InAs/ GaAs Quantum Dot, Photodetectors

Infrared, Self Assembled InAs/ GaAs Quantum Dot, Photodetectors. Michiel C. Donker. June 23, 2005. R u G. VLWIR > 12 μ m < 0.10 eV. SWIR = 0.7 - 3 μ m 1.77 - 0.41eV. LWIR = 7 - 12 μ m 0.18 - 0.10 eV. MWIR = 3 - 7 μ m 0.41 - 0.18 eV. Infrared Light.

marlis
Download Presentation

Infrared, Self Assembled InAs/ GaAs Quantum Dot, Photodetectors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Infrared, Self Assembled InAs/ GaAs Quantum Dot, Photodetectors Michiel C. Donker June 23, 2005 RuG

  2. VLWIR > 12 μm < 0.10 eV SWIR = 0.7 - 3 μm 1.77 - 0.41eV LWIR = 7 - 12 μm 0.18 - 0.10 eV MWIR = 3 - 7 μm 0.41 - 0.18 eV Infrared Light Infrared

  3. LWIR IR Detector Applications • Medicine • Medicine • Astronomy • Astronomy • Defense • Defense • Environment • Environment 8.5 μm 0.15 eV

  4. Content • Introduction • Quantum Dots • Device Fabrication • Electronic Structure • Characterisation and Performance • Conclusion

  5. IR IR HgCdTe Detectors • Hg1-xCdxTe • Wavelength 0.7- 25 μm • High detectivity • Difficult to process 0.0495 - 1.77 eV Hole Vbias =1.0 V • Photo Current HgCdTe • Dark Current Electron

  6. z cross section GaAs InAs InAs Quantum Well 2D 50 nm Conduction band cross section GaAs: Eg= 1.52 eV E cross section GaAs InAs GaAs GaAs InAs: Eg =0.36 eV InAs GaAs Valence band InAs Quantum Dot 0D z Quantum Wire 1D Quantum Confinement InAs Bulk 3D

  7. Density of States Bulk Quantum Well Quantum Wire Quantum Dot g(E)= density of states

  8. < Ψi I r I Ψj > = 0 111 211 x=0 x=L Quantum Dot: Particle in a Box • Infinite potential barrier • Ψ~ sin(nπx/ Lx) sin(mπy/ Ly) sin(lπz/ Lz) • Selection rules: 1-D

  9. InAs GaAs Heavely n- doped GaAs InAs Heavely n- doped GaAs Self Assembled Quantum Dots • Host: GaAs 5.653 Å • Quantum Dot: InAs 5.867 Å • Stranski- Krastanov growth GaAs

  10. IR IR GaAs conduction band Wetting Layer 128 meV d 121 meV 115 meV IR 63 meV p 100010 56 meV s 000 0 meV 930 meV 0 meV h 000 31 meV h 100010 55 meV h 110 57 meV h 200 61 meV h020 Wetting Layer GaAs 3D valence band Electronic Structure • Lens shaped QD’s • Pyrimidal QD’s S.Sauvage et al. C.R. Physique 4, p1133 (2003)

  11. Conduction band Conduction Band edge S  P transition S  P transition S  wetting layer, conduction band Characterisation • Intersubband: absorption e  e Δn=odd non zero Δn=even zero In plane as well as normal incidence absorption S.Sauvage et al. C.R. Physique 4, p1133 (2003)

  12. IR Vbias Dark and Photo Current • Thermionic emission • Tunneling • Thermally assisted tunneling • Thermal generation e/ h pair GaAs conduction band Energy InAs wetting layer • Wetting layer • Conduction band • Bound state z direction

  13. phonon (lattice vibration) e-e scattering e-h scattering phonon phonon IR Capture Probability Carrier relaxation processes: GaAs • recombination D ΔE= h c/ λcut off P S The more electrons in a QD, the more charge. E GaAs InAs z

  14. 77 K Vbias (V) H.C. Liu, Opto Electronic Review 11, p.1-5 (2003) y z · xy x z S.Sauvage et al. C.R. Physique 4, p1133 (2003) Dark and Photo Current • Thermal generation • Tunneling • Number of electrons per QD • QD density • Number of QD layers • Capture probability Dark 20 K • Angle of incidence • Shape and size • Absorption cross section • Vbias D.Pang et el. Appl. Phys. Lett. 75, p. 2719 (1999)

  15. - η = quantum efficiency = # generated electrons by photons # incident photons τ carrier lifetime - g = gain == # carriers through device # generated carriers by photons τcarrier transit time Iphotocurrent Poptical power e η g h v Responsivity and Detectivity • Responsivity (mA/ W) == • Detectivity (cm Hz1/2/ W) = signal to noise ratio • Background photon noise • Photo electron noise; detectable carrier η, not detectable (1- η) • Receiver circuit noise

  16. Responsivity (A/ W) 165 eV Wavelength (μm) Responsivity and Detectivity Iphotocurrent • Responsivity (mA/ W) = Poptical power L. Jiang et al. Appl. Phys. Lett. 82, p.1986 (2003) • Detectivity (cm Hz1/2/ W) = signal to noise ratio 77 K Vbias= -2.0 V QD density = 1.2 x 1010 Size 26 nm 6 nm D = 3.6 x 1010 cm Hz1/2/ W

  17. xy Vbias z Conclusion • QD: D = 3.6 x 1010 cm Hz1/2/ W • HdCdTe: D = 2.2 x 1012 cm Hz1/2/ W • # electrons per dot • dot density • dot size and shape • spacing thickness • transport direction J.Philips et al. Encyclopedia of Nanoscience and Nanotechnology, 9 p. 131 (2004)

  18. Acknowledgements Paul van Loosdrecht Quantum Well Camera

  19. < Ψi I r I Ψj > = 0 Δn=odd, on the same axis 000  100 100  010 100  200 000  200 X X <1 | z | 2>= (16/9π2)/L <1 | z | 4>= (4/45π2)/L x=0 x=L Questions • Infinite potential barrier • Ψ~ sin(nπx/ L) sin(mπy/ L) sin(lπz/ L) • Selection rules: • Fermi golden rule:

  20. Intersubband selection rules: e  e Δn=odd strong Δn=even zero Interband selection rules: h  e Δn=0 strong Δn=0 odd weak Δn=0 even zero H 000  E 000 Questions • Interband: Photo Luminescense • Intersubband: Absorption S.Sauvage et al. C.R. Physique 4, p1133 (2003)

  21. | <n0| k·p |j0> |2 En(0) – Ej (0) Questions • D= R AΔf / Inoise • H= Hk·p + Hstrain + Vconfining potential • En (k) = En (0) + h2k2/2m + h2/m2Σ’ n= band index

  22. Vbias Questions GaAs GaAs AlGaAs AlGaAs InAs E z

  23. Questions L. Jiang et al. APL 82, p.1986 (2003)

  24. Questions S.F. Tang et al. APL 78, p. 2428 (2001)

  25. Questions

More Related