visione nell’infrarosso e qwip quantum-well infrared photodetectors visione nell’infrarosso e...
TRANSCRIPT
![Page 1: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/1.jpg)
Visione nell’infrarossoVisione nell’infrarosso ee
QWIP QWIPQuantum-Well Infrared PhotodetectorsQuantum-Well Infrared Photodetectors
Docente: Mauro MoscaDocente: Mauro Mosca
(www.dieet.unipa.it/tfl)(www.dieet.unipa.it/tfl)
Università di Palermo – Scuola Politecnica - DEIM
A.A. 2014-15A.A. 2014-15
![Page 2: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/2.jpg)
Un po’ di storia: esperimento di HerschelUn po’ di storia: esperimento di Herschel
1800
![Page 3: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/3.jpg)
Un po’ di storia: termopila di Nobili-MeloniUn po’ di storia: termopila di Nobili-Meloni
1829… arrivano i rivelatori
![Page 4: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/4.jpg)
Un po’ di storia: primo tubo Un po’ di storia: primo tubo convertitore d’immaginiconvertitore d’immagini
first photon effect (selenium) by Smith in 1873
seconda guerra mondiale… visione al buio
galena (PbS)-metal diode by Braun in 1874
IR photoconductivity of Tl2S by Case in 1917
Cs−O−Ag photocathode (S−1)
![Page 5: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/5.jpg)
Sviluppo dei sistemi di rivelazione IRSviluppo dei sistemi di rivelazione IR
seriale parallelo
![Page 6: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/6.jpg)
Eccitazione ottica nei semiconduttoriEccitazione ottica nei semiconduttori
generazione termica comparabile a quella ottica
![Page 7: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/7.jpg)
Rivelatori termici e fotoniciRivelatori termici e fotonici
![Page 8: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/8.jpg)
Detectivity di vari rivelatori IRDetectivity di vari rivelatori IR
![Page 9: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/9.jpg)
BLIP BLIP ((background-limited infrared photodetection)background-limited infrared photodetection)
Problema della background radiationProblema della background radiation
G = GG = Gthth + + GGoptopt
The optical generation may be due to the The optical generation may be due to the signal or background radiation.signal or background radiation.If the thermal generation is reduced much If the thermal generation is reduced much below the background level, the below the background level, the performance of the device is determined performance of the device is determined by the background radiation (BLIP)by the background radiation (BLIP)
For the BLIP requirements: For the BLIP requirements: GGoptopt > > GGthth
![Page 10: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/10.jpg)
FPA: prima generazioneFPA: prima generazione
US common module HgCdTe arrays employ60, 120 or 180 photoconductive elements
![Page 11: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/11.jpg)
FPA: seconda generazioneFPA: seconda generazione
pixel deselecting, antiblooming on each pixel, subframe imaging, output preamplifiers
~ 7 m
example: HgCdTe multilinear 288×4 arrays (Sofradir)
eccessiva esposizione: glielettroni debordano e un’interaarea dell’immagine appare bianca
![Page 12: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/12.jpg)
FPA ibridoFPA ibrido
CdTe, CdZnTe(max chip size 10 mm2)
PACE(Producible Alternative to CdTe for Epitaxy)
![Page 13: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/13.jpg)
Evoluzione pixels per arrayEvoluzione pixels per array
![Page 14: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/14.jpg)
Why HgCdTe?Why HgCdTe?
- Problems in mass production, which result from a weak Hg–Te bond
- Health hazard (toxic compounds)
- High mercury vapour pressure over melts
- Difficulties in repeatable growth of uniform composition bulk crystals and epitaxial layers
but…
- Can be tailored for optimised detection at any region of IR spectrum (1-25 m)
- HgCdTe is the only material covering the whole IR spectral range having nearly the same lattice parameter
- The difference of lattice parameter between CdTe andHg0.8Cd0.2Te is 0.2%. Replacing small fraction of Cd with Zn or Te with Se can compensate the residual latticemismatch.
![Page 15: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/15.jpg)
HgCdTe: gap vs. lattice constantHgCdTe: gap vs. lattice constant
![Page 16: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/16.jpg)
Fotodiodi HgCdTe (illuminati dall’alto)Fotodiodi HgCdTe (illuminati dall’alto)
![Page 17: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/17.jpg)
Fotodiodi HgCdTe (illuminati dall’alto)Fotodiodi HgCdTe (illuminati dall’alto)
![Page 18: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/18.jpg)
Fotodiodi HgCdTe (illuminati dal basso)Fotodiodi HgCdTe (illuminati dal basso)
![Page 19: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/19.jpg)
Fotodiodi HgCdTe (illuminati dal basso)Fotodiodi HgCdTe (illuminati dal basso)
![Page 20: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/20.jpg)
Diagramma a bande di una Diagramma a bande di una omogiunzione omogiunzione n+ n+ onon p p
trasparente
![Page 21: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/21.jpg)
Assorbimento intersubbandaAssorbimento intersubbanda
interbanda interSUBbanda
![Page 22: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/22.jpg)
nn-doped bound-to-bound QWIP-doped bound-to-bound QWIP
trasporto perpendicolare(mobilità dello stato eccitato più alta)
si blocca la dark current dovuta alle carichedel ground-state
tunneling
le eterobarriere bloccano il tra-sporto delle cariche nel ground-state
![Page 23: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/23.jpg)
nn-doped bound-to-continuum QWIP-doped bound-to-continuum QWIP
no tunneling
per ottenere ilcontinuum si deverestringere lalarghezza della well
la barriera si può allargaresenza far diminuire la fotocorrente
ground-statecurrent
si può diminuire la V di polarizzazione equindi abbassare la dark current
![Page 24: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/24.jpg)
nn-doped bound-to-quasibound QWIP-doped bound-to-quasibound QWIP
barriera per l’emissione termoionica(dark current) = barriera per
la fotocorrente
la barriera sale di ca. 15 meV rispetto al caso continuo
Lo stato eccitato si innalza al diminuire di Lw
ma appena sale al continuum la barriera diminuisce
![Page 25: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/25.jpg)
nn-doped broadbound QWIP-doped broadbound QWIP
progettati perdiverse
quasibound
si può sostituire con un super-reticolo
![Page 26: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/26.jpg)
nn-doped bound-to-bound miniband QWIP-doped bound-to-bound miniband QWIP
super-reticolo riduce la ground-statedark current
la fotocorrente passa
la dark current NO!
rivela a ca. 0 V bias (tunneling)
quando le larghezze delle barriere diventano comparabilicon quelle delle quantum-wells…
le funzioni d’onda delle singole wells si sovrappongonoa causa del tunneling…
formazione di MINIBANDEMODESTA DETECTIVITY (109 Jones)
bassa efficienza di raccolta
solo gli elettroni eccitati in corrispondenza delle QW vicinoall’elettrodo di raccolta contribuiscono alla corrente
![Page 27: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/27.jpg)
nn-doped bound-to-continuum miniband QWIP-doped bound-to-continuum miniband QWIP
migliora iltrasportodeglielettronieccitati
aumentala darkcurrenttermo-ionica
![Page 28: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/28.jpg)
nn-doped bound-to-miniband QWIP-doped bound-to-miniband QWIP
come bound-to-continuum (ma minore mobilità perché gli elettroni possono essere catturati in una QW)
dark current relativamente alta
![Page 29: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/29.jpg)
nn-doped step bound-to-miniband QWIP-doped step bound-to-miniband QWIP
si riduce la dark current (più barriere da attraversare)
InGaAs.strained quantum wells(più profonde delle barriere del super-reticolo)
![Page 30: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/30.jpg)
Dark currentDark current
tunneling (T<30 K)
thermal-assistedtunneling (30<T<55 K)
thermoionic emission(T>55 K)
![Page 31: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/31.jpg)
Risposta spettraleRisposta spettrale
Unlike the responsivity spectrums of intrinsic infrared detectors, the responsivity spectrums of QWIPS aremuch narrow and sharper
due to their resonance intersubband absorption.
larger
![Page 32: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/32.jpg)
Risposta spettraleRisposta spettrale
![Page 33: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/33.jpg)
Risposta spettraleRisposta spettrale
ground state-barrierresonance
At low bias the responsivity is nearly linearly dependent on biasand it saturates at high bias
This saturation is due to the saturation of carrier drift velocity
at lower bias voltageescape probability of
the photoexcitedelectrons at the
bounded firstexcited state
is much smaller
![Page 34: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/34.jpg)
Accoppiamento della luce: Accoppiamento della luce: random reflectorrandom reflector
E
QWIPs do not absorb radiation incident normal to the surface since the light polarization must have an electric field component normal to the superlattice (growth direction) to be absorbed by the confined carriers
![Page 35: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/35.jpg)
Accoppiamento della luce: reticolo 2DAccoppiamento della luce: reticolo 2D
![Page 36: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/36.jpg)
Applicazioni QWIP: regime MWIR e LWIRApplicazioni QWIP: regime MWIR e LWIR
maximum blackbodyemission at
300 K
maximum thermal contrast
![Page 37: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/37.jpg)
MWIR LWIR
Applicazioni QWIP: regime MWIR e LWIRApplicazioni QWIP: regime MWIR e LWIR
![Page 38: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/38.jpg)
Applicazioni QWIP: visione Applicazioni QWIP: visione dual band IRdual band IR
LWIR emission is very sensitive to the surface roughness
![Page 39: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/39.jpg)
Applicazioni QWIP: campi minatiApplicazioni QWIP: campi minati
1
2
![Page 40: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/40.jpg)
![Page 41: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/41.jpg)
![Page 42: Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Visione nell’infrarosso e QWIP Quantum-Well Infrared Photodetectors Docente: Mauro](https://reader035.vdocuments.pub/reader035/viewer/2022062404/5542eb76497959361e8e06c1/html5/thumbnails/42.jpg)