Quantum Dot Infrared Photodetector - PowerPoint PPT Presentation

1 / 15
About This Presentation
Title:

Quantum Dot Infrared Photodetector

Description:

What is a Photo-detector? ... A photo-detector is an opto-electronics device ... American Science & Engineering Billerica, Ma. Prof: Sam Milshtein UMass Lowell ... – PowerPoint PPT presentation

Number of Views:1421
Avg rating:3.0/5.0
Slides: 16
Provided by: Keo
Category:

less

Transcript and Presenter's Notes

Title: Quantum Dot Infrared Photodetector


1
Quantum Dot Infrared Photo-detector
  • 16.508 Quantum Electronics for Engineer
  • Present by Chintana Keo
  • Date May 3, 2006

2
Agenda
  • What is a Photo-detector?
  • What is the different between Quantum Dot
    Infrared Photo-detector (QDIP) and Quantum Well
    Infrared Photo-detector (QWIP)?
  • Sample sketch or diagram of QDIP
  • How does the device work?
  • Advantage of QDIP
  • Dark current calculation Why?
  • Detection energy calculation
  • Some possible applications
  • Conclusion

3
What is a photo-detector?
  • A photo-detector is a semi-conductor photodiode
    device that generate electrical current or
    electrons excitation when light source is shine
    onto its surface or when light source is
    entering a diode semiconductor device made from
    such material as GaAs InGaAs.
  • A photo-detector is an opto-electronics device
    that allow us to produce an image of an object as
    a result of the electrical current produced by
    shining a light source within a given wavelength
    range depending on what materials is used.

4
What is a photo-detector? (Continues)
  • A photo-detector is basically a photodiode in
    principle. When struck by light source, the
    electrons within become stimulated and create
    current across a diode resulting in an exact
    duplicated image as the source.

5
The different between quantum well quantum dot
  • There similarities and different characteristics
    of photo detectors
  • Quantum Well Infrared Photo-Detector (QWIP)
  • Quantum Dot Photo-Detector (QDIP).
  • Figure shows the different between quantum dot
    and quantum well
  • Left is quantum well infrared photo-detector
  • Well between barriers
  • Right is quantum dot infrared photo-detector
  • Dots between barriers

6
Schematic Sample of Quantum Dot
  • Boron doped Ge quantum dots growth sample
  • Producing using molecular-beam epitaxy (MBE)
    method in a thin layer of semi-conductor
    materials.

7
Basic Device
  • Both device has an emitter and a collector
  • The detection mechanism in both devices is by
    intraband photo excitation of electrons between
    energy levels

8
The Advantage of QDIP
  • QDIP allow direct incident normal to wafer
    surfaces.
  • Avoid fabricating grate coupler as in QWIP.
  • In producing QWIP, a grating coupler required
    which yield in extra fabrication steps.
  • It has lower dark current high detection
    sensitivity than QWIP.
  • Better Radiant sensitivity and Efficiency
    resulting in better detection.
  • Dominant in normal direction response to growth
    direction.

9
Dark Current Calculation
  • Dark current is the current produce internal to
    the photodetector resulting as noise
  • Simplest way to calculate dark current density is
    to count mobile carrier barrier and carrier
    velocity
  • Jdark is a dark current
  • ? is a drift velocity
  • n3d is current density
  • Can be calculate using the second formula at
    left.
  • mb is a barrier effective mass
  • Ea is thermal activation energy

10
Radiant Sensitivity and Quantum Efficiency
  • Current produce when light hitting a
    semi-conductor radiating electrons excitation.
  • This can be calculate using the following formula
  • QE ((S x 1240) / ? ) x 100
  • Where S is the radiant sensitivity
  • Long exited electron lifetime lead to high
    responsivity, higher temp and higher dark current
    which will limited detectivity

11
Responsivity
  • Responsivity can be calculated using the formula
    at left, where
  • ? - a phonon frequency
  • ? - the absorption efficiency
  • g - photoconductive gain
  • Higher absorption efficiency have better
    detection.

12
Possible Applications
  • High speed infrared detection
  • Infrared image applicationpossible use in
    security systems to produce image of various
    objects.
  • Possible use in IR Spectrophotometer
  • Possible use in Cell Sorter
  • Could be use in Infrared Camera

13
Conclusion
  • There are still many challenges to overcome such
    fabrication or manufacturing process that will
    produce quantum dot to meet design requirement
  • Current manufacturing process limit to size and
    dot density that it is impractical for commercial
    used
  • Due to complex fabrication process and limited
    size it is expensive to manufacture
  • Still in its infancyneeds better doping control

14
Question?
  • Thank You

15
Credit Reference
  • Prof Joel TherrienUMass Lowell.
  • American Science EngineeringBillerica, Ma
  • Prof Sam MilshteinUMass Lowell
  • PhotodiodesHamamatsu Photonics K.K. Solid State
    Division
  • The Photonics Dictionary, 42nd Ed 1996The Tropel
    Spectrum
  • Growth Study of Surfactant-Mediate SiGe graded
    layersThin Solid Film 380 (2000) 54-56
  • Photoluminescence of multi-layer of SiGe dot
    growth on SiJ. Wa, H LouDevice research
    laboratory, Electrical Engineering
    Department---University of California at Los
    Angeles
  • Reshifting and broadening of quantum well
    infrared photo-detectorIEEE Journal of selected
    topic in quantum electronics, vol 4 No 4
    July/August 1998
  • Intersuband absorption in boron dope multiple Ge
    Quantum DotApplied Physic Letter Vol. 74, Number
    2, January 11, 1998
  • Normal Incidence Mid-Range Ge Quantum dot
    photo-detectorFei Lou, Song Tong, Jianlin Liu
    Kang L. Wang--Journal of Electronics materials,
    vol. 33, Number 8, 2004
  • Zhen Yang, Yi Shi, Jianlin Liu, Bo Yan, Rang
    Zhang, Youdou Zhen Kanglong WangOptical
    Properties of Ge/Si quantum dot
    superlaticesDepartment of Physic and National
    Laboratory of Solid State Microstructure, Nanjing
    University University of California. Science
    DirectMaterial Letters 58 (2004) 3765-3768
Write a Comment
User Comments (0)
About PowerShow.com