Transcript "Photoluminescent Properties of InGaAs Quantum Dot Structures"

PHOTOLUMINESCENT
PROPERTIES OF InGaAs
QUANTUM DOT STRUCTURES
Kenneth Clark, John Colton, Matt Guerron, Dallas Smith, Scott Thalman
Brigham Young University
Haeyeon Yang
Utah State University
Quantum Dots
GaAs
InGaAs
GaAs
Dong Jun Kim et al 2008
Nanotechnology 19 47560
Grown on surface
with molecular beams
http://uwnews.org/uweek/article.aspx?id=42599
Chemically grown in solution
Photoluminescence (P.L.)
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Spectroscopy
Lock-in Amplifier
BNC Cable
Monochromator
Cryostat
Lenses
Detector
Sample
Focusing Lens
Mirror
Chopper
Power Controller
The Experiment
032607B, 3.7K, 50% Duty, 3s Tau, 780nm
Quantum Dots
P.L. (Arbitrary Units)
1E-9
Indium Rich
Regions
1E-10
50 mW
1E-11
Wetting Layer
1000
1200
1400
Wavelength (nm)
Wavelength
W. Chang et al (1999 )
Scan Results
Sample 032607B
Problem:
Peaks shift giving
Laser at 780nm
Inaccurate scan results.
P.L (arb. units)
1E-9
1E-10
250mW
240mW
230mW
160mW
80mW
1E-11
Reason: Higher excitation energy
800
causes sample
heating.1000
1200
Wavelength (nm)
1400
The Solution
Duty Cycle decreased from 50% to 8.33%
Power (Arbitrary Units)
Sample 032607B, 3K, 780nm, 8% Duty, .3s Tau
Files 8,9,12,13
260mW (1927.4W/cm^2)
200mW (1482.6W/cm^2)
Ability to use higher
160mW (1186W/cm^2)
120mW (889.5W/cm^2)
Excitation energies
1E-11
Sample 032607B
Laser at 780nm
1E-12
Less signal, meaning lower
intensity readings.
1000
P.L (arb. units)
1E-9
1E-10
1E-11
1200
Wavelength (nm)
800
250mW
240mW
230mW
160mW
80mW
1400
1000
1200
Wavelength (nm)
1400
In Conclusion
 These samples have strong P.L.
 Adjust growth technique
 P.L. up to 1400nm even at
room temperature
 Patterned samples
September 9, 2010 Sample 032607B
0.10
Light Source: 780nm, 50 mW
Detector: PDF 10C
Chop: 20 Hz, 50% Duty
0.08
Spec: Grating C
P.L. (V)
Lock-in: V-mode, tau=0.3s
File 2
0.06
0.04
0.02
100nm
0.00
800
1000
1200
1400
Wavelength (nm)
1600
1800
Yang et al., submitted to Nanoletters