Quantum Dot Infrared Quantum Dot Infrared Photo-detectorPhoto-detector

16.508 Quantum Electronics for Engineer16.508 Quantum Electronics for Engineer

Present by:Present by: Chintana Keo Chintana Keo

Date: May 3, 2006Date: May 3, 2006

AgendaAgenda

What is a Photo-detector?What is a Photo-detector?What is the different between Quantum Dot Infrared What is the different between Quantum Dot Infrared Photo-detector (QDIP) and Quantum Well Infrared Photo-detector (QDIP) and Quantum Well Infrared Photo-detector (QWIP)?Photo-detector (QWIP)?Sample sketch or diagram of QDIPSample sketch or diagram of QDIPHow does the device work?How does the device work?Advantage of QDIPAdvantage of QDIPDark current calculation & Why?Dark current calculation & Why?Detection energy calculationDetection energy calculationSome possible applicationsSome possible applicationsConclusionConclusion

What is a photo-detector?What is a photo-detector?

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

What is a photo-detector? (Continues)What is a photo-detector? (Continues)

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

The different between quantum well & The different between quantum well & quantum dotquantum dot

There similarities and different There similarities and different characteristics of photo detectors:characteristics of photo detectors:

Quantum Well Infrared Photo-Quantum Well Infrared Photo-Detector (QWIP)Detector (QWIP)

Quantum Dot Photo-Detector Quantum Dot Photo-Detector (QDIP).(QDIP).

Figure shows the different Figure shows the different between quantum dot and between quantum dot and quantum well:quantum well:Left is quantum well infrared Left is quantum well infrared photo-detectorphoto-detector

Well between barriersWell between barriers

Right is quantum dot infrared Right is quantum dot infrared photo-detectorphoto-detector

Dots between barriersDots between barriers

Schematic Sample of Quantum DotSchematic Sample of Quantum Dot

Boron doped Ge Boron doped Ge quantum dots growth quantum dots growth samplesample

Producing using Producing using molecular-beam epitaxy molecular-beam epitaxy (MBE) method in a thin (MBE) method in a thin layer of semi-conductor layer of semi-conductor materials.materials.

Basic DeviceBasic Device

Both device has an Both device has an emitter and a collectoremitter and a collector

The detection The detection mechanism in both mechanism in both devices is by intraband devices is by intraband photo excitation of photo excitation of electrons between electrons between energy levelsenergy levels

The Advantage of QDIPThe Advantage of QDIP

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

Dark Current CalculationDark Current Calculation

Dark current is the current Dark current is the current produce internal to the produce internal to the photodetector resulting as noisephotodetector resulting as noiseSimplest way to calculate dark Simplest way to calculate dark current density is to count mobile current density is to count mobile carrier barrier and carrier velocitycarrier barrier and carrier velocity

JJdarkdark is a dark current is a dark current

υυ is a drift velocity is a drift velocity

nn3d3d is current density is current density Can be calculate using the second Can be calculate using the second

formula at left.formula at left.

mmbb is a barrier effective mass is a barrier effective mass

EEaa is thermal activation energy is thermal activation energy

Radiant Sensitivity and Quantum Radiant Sensitivity and Quantum EfficiencyEfficiency

Current produce when light hitting a semi-Current produce when light hitting a semi-conductor radiating electrons excitation.conductor radiating electrons excitation.This can be calculate using the following This can be calculate using the following formulaformulaQE = ((S x 1240) / QE = ((S x 1240) / λλ ) x 100% ) x 100% Where S is the radiant sensitivityWhere S is the radiant sensitivity

Long exited electron lifetime lead to high Long exited electron lifetime lead to high responsivity, higher temp and higher dark responsivity, higher temp and higher dark current which will limited detectivitycurrent which will limited detectivity

ResponsivityResponsivity

Responsivity can be Responsivity can be calculated using the calculated using the formula at left, where:formula at left, where: υυ - a phonon frequency - a phonon frequency ηη - the absorption - the absorption

efficiencyefficiency g - photoconductive gaing - photoconductive gain

Higher absorption Higher absorption efficiency have better efficiency have better detection.detection.

Possible ApplicationsPossible Applications

High speed infrared detectionHigh speed infrared detection

Infrared image application—possible use in Infrared image application—possible use in security systems to produce image of various security systems to produce image of various objects.objects.

Possible use in IR SpectrophotometerPossible use in IR Spectrophotometer

Possible use in Cell SorterPossible use in Cell Sorter

Could be use in Infrared CameraCould be use in Infrared Camera

ConclusionConclusion

There are still many challenges to overcome such There are still many challenges to overcome such fabrication or manufacturing process that will fabrication or manufacturing process that will produce quantum dot to meet design requirementproduce quantum dot to meet design requirement

Current manufacturing process limit to size and dot Current manufacturing process limit to size and dot density that it is impractical for commercial useddensity that it is impractical for commercial used

Due to complex fabrication process and limited size it Due to complex fabrication process and limited size it is expensive to manufactureis expensive to manufacture

Still in its infancy—needs better doping controlStill in its infancy—needs better doping control

Question?Question?

Thank YouThank You

Credit & ReferenceCredit & ReferenceProf: Joel Therrien—UMass Lowell.Prof: Joel Therrien—UMass Lowell.American Science & Engineering—Billerica, MaAmerican Science & Engineering—Billerica, MaProf: Sam Milshtein—UMass LowellProf: Sam Milshtein—UMass LowellPhotodiodes—Hamamatsu Photonics K.K. Solid State DivisionPhotodiodes—Hamamatsu Photonics K.K. Solid State DivisionThe Photonics Dictionary, 42The Photonics Dictionary, 42ndnd Ed 1996—The Tropel Spectrum Ed 1996—The Tropel SpectrumGrowth Study of Surfactant-Mediate SiGe graded layers—Thin Solid Film 380 (2000) 54-56Growth Study of Surfactant-Mediate SiGe graded layers—Thin Solid Film 380 (2000) 54-56Photoluminescence of multi-layer of SiGe dot growth on Si—J. Wa, H Lou—Device research Photoluminescence of multi-layer of SiGe dot growth on Si—J. Wa, H Lou—Device research laboratory, Electrical Engineering Department---University of California at Los Angeleslaboratory, Electrical Engineering Department---University of California at Los AngelesReshifting and broadening of quantum well infrared photo-detector—IEEE Journal of selected Reshifting and broadening of quantum well infrared photo-detector—IEEE Journal of selected topic in quantum electronics, vol 4 No 4 July/August 1998topic in quantum electronics, vol 4 No 4 July/August 1998Intersuband absorption in boron dope multiple Ge Quantum Dot—Applied Physic Letter Vol. Intersuband absorption in boron dope multiple Ge Quantum Dot—Applied Physic Letter Vol. 74, Number 2, January 11, 199874, Number 2, January 11, 1998Normal Incidence Mid-Range Ge Quantum dot photo-detector—Fei Lou, Song Tong, Jianlin Normal Incidence Mid-Range Ge Quantum dot photo-detector—Fei Lou, Song Tong, Jianlin Liu & Kang L. Wang--Journal of Electronics materials, vol. 33, Number 8, 2004Liu & 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 Wang—Zhen Yang, Yi Shi, Jianlin Liu, Bo Yan, Rang Zhang, Youdou Zhen & Kanglong Wang—Optical Properties of Ge/Si quantum dot superlatices—Department of Physic and National Optical Properties of Ge/Si quantum dot superlatices—Department of Physic and National Laboratory of Solid State Microstructure, Nanjing University & University of California. Laboratory of Solid State Microstructure, Nanjing University & University of California. Science Direct—Material Letters 58 (2004) 3765-3768Science Direct—Material Letters 58 (2004) 3765-3768