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Investigation of Noise in Quantum Dot Structures

Investigation of Noise in Quantum Dot Structures. Tim Morgan. Quantum Dot Devices. Optoelectronics. Infrared Pictures. Optimized Device. InAs/InGaAs QDs. http://cqd.eecs.northwestern.edu/research/qdots.php. Biosensors. Igor L. Medintz, et. al. Nature Materials 2003. Research Plan.

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Investigation of Noise in Quantum Dot Structures

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  1. Investigation of Noise in Quantum Dot Structures Tim Morgan

  2. Quantum Dot Devices Optoelectronics Infrared Pictures Optimized Device InAs/InGaAs QDs http://cqd.eecs.northwestern.edu/research/qdots.php Biosensors Igor L. Medintz, et. al. Nature Materials 2003 QDs & Noise 9.5.07

  3. Research Plan • Capped InGaAs Quantum Dots • AFM, Hall, DLNS, PL • QDIPs • DLNS: doping, blocking barrier • Temperature dependence  defects • I-V: correlation of noise & dark current ? • C-V: Temperature dependence • PL • Open InAs & InGaAs Quantum Dots • AFM, Hall, DLNS, PL QDs & Noise 9.5.07

  4. Capped InGaAs QD Structure Sample # MLs 1500 Å GaAs: Si T=1133ºC S1 0 200 Å GaAs: undoped S2 6 S3 9 InGaAs QD layer S4 11 200 Å GaAs: undoped S5 13 5000 Å GaAs: Si T=1133ºC 5000 Å GaAs buffer GaAs (001) SI What is the relationship between noise and QDs? QDs & Noise 9.5.07

  5. QD Profiles • No QDs with 6 ML (RHEED, Mobility) 9 ML Height: 4.77 ± 1.14 nm Lateral Size: 36.47 ± 6.26 nm Density: 1.73 × 107 cm-2 11 ML Height: 7.05 ± 1.35 nm Lateral Size: 36.89 ± 8.08 nm Density: 4.00 × 107 cm-2 13 ML Height: 7.15 ± 1.45 nm Lateral Size: 47.52 ± 9.31 nm Density: 3.18 × 107 cm-2 QDs & Noise 9.5.07

  6. Sample Preparation 270 nm Au 20 nm Ni 75 nm AuGe 30 µm Greek Cross • Wet Etch • Metallization • Annealing  Lower Contact Resistance • Wire Bonding  Packaging QDs & Noise 9.5.07

  7. Hall Measurement • 6 ML Sample yields largely different Hall data • 0 ML has higher mobility than QDs QDs & Noise 9.5.07

  8. Deep Level Noise Spectroscopy • Thermal Noise • Flicker (1/f) Noise • Generation-Recombination Noise QDs & Noise 9.5.07

  9. 0 ML Sample T = 294 K T = 82 K QDs & Noise 9.5.07

  10. 6 ML Sample T = 294 K T = 82 K QDs & Noise 9.5.07

  11. 9 ML Sample T = 294 K T = 82 K QDs & Noise 9.5.07

  12. 11 ML Sample T = 294 K T = 82 K QDs & Noise 9.5.07

  13. 13 ML Sample T = 294 K T = 82 K QDs & Noise 9.5.07

  14. Constant Frequency f = 50 Hz QDs & Noise 9.5.07

  15. Constant Frequency f = 500 Hz QDs & Noise 9.5.07

  16. Constant Frequency f = 5000 Hz QDs & Noise 9.5.07

  17. Constant Frequency f = 50 Hz QDs & Noise 9.5.07

  18. Constant Frequency f = 500 Hz QDs & Noise 9.5.07

  19. Constant Frequency f = 5000 Hz QDs & Noise 9.5.07

  20. Monolayers f = 50 Hz QDs & Noise 9.5.07

  21. Monolayers f = 500 Hz QDs & Noise 9.5.07

  22. Monolayers f = 5000 Hz QDs & Noise 9.5.07

  23. Observations • 6 ML sample has a different trend in the Hall data, indicating behavior more in line with a quantum well • Reference has highest mobility at peak • Noise in samples with QDs is less than reference • Seen on Monolayer, I2, and E plots QDs & Noise 9.5.07

  24. For the Future • Calculate the Hooge parameter to compare flicker noise between samples • Analyze G-R noise using Temperature Dependent data • Calculate activation energies using Arrhenius plots • Package & Measure QDIPs, InAs open QDs, InGaAs open QDs QDs & Noise 9.5.07

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