2012-02-15 GEL 4203 / GEL 7041 OPTOÉLECTRONIQUE Auxiliaire d enseignement Nicolas Ayotte GEL 4203 / GEL 7041 Optoélectronique
VI PN JUNCTION The density of charge sign Fixed charge density remaining 2
VIII STRUCTURE OF LIGHT DETECTORS 1. Typical photodiode 2. PIN photodiode 3. Solar cell 4. Avalanche photodiode 5. Phototransistor 6. CCD and CMOS arrays 3
VIII.1 TYPICAL PHOTODIODE Typical photodiode Sufficient photon energy V r Reverse biased Dark current (a) Electrode SiO 2 p + I ph R V out AR coating h> E g h + e n E Antireflection coating W Electrode Depletion region (b) 1999 net S. O. Kasap, Optoelectronics (Prentice Hall) en d x 4
VIII.2 PIN PHOTODIODE PIN Intrinsic region Improves collection Decreases capacity Excellent responsivity Large bandwidth (~> 30 GHz) Vj en w en w en w 2 2 2 2 wi a p a p d n SiO 2 Electrode p + Electrode i-si n + (a) (b) en d en a net 2 2V j 1 1 w wi e Na Nd 1999 S. O. Kasap, Optoelectronics (Prentice Hall) x E(x) 5
VIII.3 SOLAR CELL Solar cell Operated as electrical power source Forward bias Reverse current Overall efficiency of ~20-30% Use of multi-junction 20 1999 S. O. Kasap, Optoelectronics (Prentice Hall) I (ma) Dark 0 I ph 0.2 0.4 V oc 0.6 V Light 20 Twice the light 6
GEL 4203 / GEL 7041 Optoélectronique 2012-02-15 Consider photon flux density vs. power density Si 7
VIII.3 SOLAR CELL IV and PV curves 8
GEL 4203 / GEL 7041 Optoélectronique 2012-02-15 VIII.3 SOLAR CELL Electrical efficiency él P P él opt V p P I p opt Fill Factor Usually about 60%-70% FF P V max oc I sc V V p oc I I p sc 9
VIII.4 AVALANCHE PHOTODIODE Electrode SiO 2 E I p h R Impact ionization h > E g n + p e h + p p + ( a ) Electrons impact-ionize covalent bonds in p layer Intrinsic gain More than one EHP per photon I MI L, APD L n e t Electrode x ( b ) Excess noise, F e 2 SI f 2eM FeI L L 1999 S. O. Kasap, Optoelectronics (Prentice Hall) E ( x ) Absorption region Avalanche region x ( c ) 10
VIII.4 AVALANCHE PHOTODIODE 11
VIII.5 PHOTOTRANSISTOR Intrinsic gain Photocurrent is base current NPN or PNP construction Low noise, high gain Slow PerkinElmer Optoelectronics 12
VIII.5 PHOTOTRANSISTOR optoisolator optical switch retrosensor 1997 EG&G Optoelectronics 13
Large scale integration of detector matrix Charge-coupled devices (CCD) Costly, low noise, power consuming, higher quality World s best: CCD: 38.4k 38.4k pixels Hawaii, Pan-STARRS at 1.4 GP (Whole sky 4x/month)) 14
Large scale integration of detector matrix Complementary-metal-oxide-semiconductor (CMOS) Cheap, 100 x less noise, low-power consumption World s best : 120 megapixels @ 60 fps 202 mm x 205 mm Observatory of Kiso Observes asteroids http://videotechnology.blogspot.com 15
Copyright Fujifilm 16
Philips Photon Counter Single photon counting with 60 ps accuracy 10 cm 2, Power under 1W Copyright Philips 2010 17
F 1 >0;F 2 0;F 3 0 +V dd F 1 F metal 2 F 3 oxide p p + n AR MOS structure (-) 18
Charge generation Absorption of light in the p region Charge collection Positive voltage creates n-channel spatially localized under the oxide layer (depletion of holes) Photo-generated charges drift in the p + pn structure Electrons stored in the depleted region Q I t Contribution of dark current Q IL I t I L 0 L R 2 E W L Q max 19
Charge transfer Sequential bias of the gates V F 1 F 2 F 3 t Diffusion of carriers D, n W 2 D n 20
Charge measurement Charges reach the drain (n) Charge packet output current Integration time vs. readout time Pixel rate vs. frame rate Measurement modes Sequential Snapshot (i.e. synchronised) T T t t N t r 2 t r 21
Noise processes Shot noise, s Q Random number of accumulated charges s Q Q Read-out noise, s r Storage noise Random fluctuations of accumulated charges (+/-) Transfer noise Non-ideal transfer efficiency s 2 2 s Q s r 22
CCD D. Litwiller, CCD vs. CMOS: Facts and Fiction, Photonics Spectra, Jan. 2001 Most functions take place on the camera s PCB 23
CMOS D. Litwiller, CCD vs. CMOS: Facts and Fiction, Photonics Spectra, Jan. 2001 Most functions are integrated into the chip 2007 Tessera 24
GEL 4203 / GEL 7041 Optoélectronique 2012-02-15 feature CCD CMOS pixel signal electron packet voltage chip signal voltage (analog) word (digital) fill factor High moderate system noise low moderate to high system complexity high low sensor complexity low high camera components PCB + chips + lens 2004 Dalsa Corporation chip + lens 25
Color measurement Color selection Bayer sensor Widely used, low cost Multilayer sensor Recent, costly e.g. Foveon X3, Canon Multisensor Superior quality B standard optical filters V R http://www.mso-jena.de/en_pro42.htm 26
Bayer sensor Layer of filters superimposed on detector matrix Filter pattern Require interpolation http://en.wikipedia.org/wiki/bayer_filter 1 red 2 green 1 blue 27
2012-02-15 http://www.foveon.com/article.php?a=69 Multilayer sensor 3 separate detecting layers All light measured for every pixel GEL 4203 / GEL 7041 Optoélectronique 28
GEL 4203 / GEL 7041 Optoélectronique 2012-02-15 Multisensor 2 optical filters 3 independent sensors All light measured for every pixel red CCD green CCD blue CCD http://en.wikipedia.org/ wiki/dichroic_prism 29