The Fantastical Discoveries of Astronomy made possible by the Wonderful Properties of II-VI Materials Presentation to the Rochester Institute of Technology Virtual Detector Workshop 26 March 2012 James W. Beletic, Ph.D. Senior Director Space & Astronomy Teledyne Imaging Sensors Crystals are excellent detectors of light • Simple model of atom – Protons (+) and neutrons in the nucleus with electrons (-) orbiting • Electrons are trapped in the crystal lattice – by electric field of protons • Light energy (or thermal energy) can free an electron from the grip of the protons, allowing the electron to roam about the crystal – creates an “electron-hole” pair. • The photocharge can be collected and amplified, so that light is detected • The photon energy required to free an Silicon crystal lattice electron depends on the material. The Astronomer’s Periodic Table 1 H 2 He METALS II III IV V VI Detector Families Si - IV semiconductor HgCdTe - II-VI semiconductor InGaAs & InSb - III-V semiconductors InAs + GaSb - III-V Type 2 Strained Layer Superlattice (SLS) Tunable Wavelength: Valuable property of HgCdTe Hg1-xCdxTe Modify ratio of Mercury and Cadmium to “tune” the bandgap energy The Golden Age of Astronomy Galileo Galilei and 2 cm refractor (1609) Hubble Space Telescope • 2.4 meter European Southern Observatory Paranal Observatory • Four 8.2 meter telescopes • Four 1.8 meter auxiliary telescopes • 4 meter infrared survey telescope • 2.6 meter optical survey telescope Orion – In visible and infrared light Orion - visible Orion – by IRAS The Eagle Nebula as seen with Hubble The Eagle Nebula as seen by HST The Eagle Nebula as seen in the infrared M. J. McCaughrean and M. Andersen, 1994 European Southern Observatory • 8.2 meter telescope Atmospheric transmission Not all of the light gets through atmosphere to ground-based telescopes Atmospheric Transmission Wavelength (microns) Common Astronomical Filters J H K L M 1.1-1.4 1.5-1.8 2.0-2.4 3.0-4.0 4.5-5.1 Atmospheric Blurring The bane of ground-based astronomy Long exposure image is called the “seeing disk” Long exposure image Binary star pair 100 Her, 14 arc sec separation (Vmag = 6.0) 10 msec frame time 14 • Quantum Efficiency = 85-90% • Dark current (145K) = 0.02 e-/pix/sec • Readout noise = 25 e- (single CDS) Infrared Detector • 1024×1024 pixels • 18 μm pitch • 1.7 μm cutoff HgCdTe • Substrate-removed HubbleHubble SpaceSpace TelescopeTelescope Stephan’s Quintet WFC3 HubbleHubble UltraUltra DeepDeep FieldField IRIR // WFC3WFC3 8787 hourhour totaltotal exposureexposure 87 hour total exposure 1.051.05 μμmm (Y)(Y) 3 infrared bands 1.25 μm (J) 1.25 μm (J) 1.05 μm (Y) 1.601.60 μμmm (H)(H) 1.25 μm (J) 1.60 μm (H) Most distant galaxy yet seen Light travelled for 13.2 billion years to reach the Earth 1.05 μm (Y) 1.25 μm (J) 1.60 μm (H) HubbleHubble UltraUltra DeepDeep FieldField IRIR // WFC3WFC3 Thermal Radiation Ultraviolet Infrared Thermal Radiation 294K 120K 50K Hubble Space Telescope 2.4-m primary mirror is kept at 70 ºF (21C, 294K) Wide-fieldWide-field InfraredInfrared SurveySurvey ExplorerExplorer (WISE)(WISE) HgCdTeHgCdTe arraysarrays forfor 22 ofof 44 infraredinfrared bandsbands TwoTwo 1024×10241024×1024 pixelpixel infraredinfrared arraysarrays 3.43.4 andand 4.64.6 μμmm bandsbands 2929 SeptemberSeptember 20112011 PressPress ReleaseRelease JamesJames WebbWebb SpaceSpace TelescopeTelescope (JWST)(JWST) Lagrange Point 2 (L2) Optimal Location for Infrared Space Telescope 6.5-m mirror Earth sunshield Lagrange Points of the Earth-Sun system (not drawn to scale!) JWSTJWST II-VIII-VI SensorsSensors NIRSpec (Near Infrared Spectrograph) <6 e- noise for 1000 sec exposure FGS (Fine Guidance Sensors) 294K294K MirrorMirror Temp.Temp. 50K50K 11 MpixelMpixel ## PixelsPixels 6363 MpixelMpixel NIRCam 1 H1R 15 H2RG (Near Infrared Camera) 1024×1024 2048×2048 Dark Current of HgCdTe Detectors 8 10 Typical InSb 107 Dark Current ~9 ~5 ~2.5 106 Dark 105 Current 104 3 Electrons 10 ~1.7 per pixel 102 per sec 10 18 micron square 1 pixel 10-1 10-2 10-3 10-4 30 50 70 90 110 130 150 170 190 210 230 Temperature (K) HgCdTe cutoff wavelength (microns) •• The The energyenergy ofof aa photonphoton isis VERYVERYsmallsmall AnAn electron-voltelectron-volt –– Energy Energy ofof SWIRSWIR (2.5(2.5 μμm)m) photonphoton isis 0.50.5 eVeV (eV)(eV) isis extremelyextremely smallsmall •• In In 55 years,years, JWSTJWST willwill taketake ~1~1 millionmillion imagesimages –– Total Total ## SWIRSWIR photonsphotons detecteddetected ≈≈3.63.6 ×× 10 101616 –– Total Total energyenergy detecteddetected ≈≈1.81.8 ×× 10 101616 eVeV 15 H2RG •• Drop Drop peanutpeanut M&MM&M®® candycandy (~2g)(~2g) fromfrom 2K×2K arrays 63 million pixels heightheight ofof 1515 cmcm (~6(~6 inches)inches) –– Potential Potential energyenergy ≈≈1.81.8 xx 10101616 eVeV 1515 cmcm peanutpeanut M&MM&M®® dropdrop isis equalequal toto thethe energyenergy detecteddetected duringduring 55 yearyear operationoperation ofof thethe JamesJames WebbWebb SpaceSpace Telescope!Telescope! HybridHybrid CMOSCMOS InfraredInfrared ImagingImaging SensorsSensors Three Key Technologies • Growth and processing of the HgCdTe detector layer • Design and fabrication of the CMOS readout integrated circuit (ROIC) • Hybridization of the detector layer to the CMOS ROIC Cosmic Rays and Substrate Removal • Cosmic ray events produce clouds of detected signal due to particle- induced flashes of infrared light in the CdZnTe substrate • Removal of the substrate eliminates the effect 2.5 μm cutoff, substrate on 1.7 μm cutoff, substrate on 1.7 μm cutoff, substrate off Substrate Removal allows HgCdTe to detect UV and Visible Light Quantum Efficiency of 2.3 micron HgCdTe Astronomy is a Time Machine Thank heavens for the finite speed of light Time The Distance “Pale Blue Dot” Sun (8 min) known as Earth Pluto (4 hrs) Proxima Centauri (4.3 light years) Andromeda Galaxy (2.9 million light years) The Big Bang (13.7 billion years ago) EdwinEdwin HubbleHubble 18891889 –– 1953 1953 WorkedWorked atat Mt.Mt. WilsonWilson Mt Wilson 100-inch telescope 19191919 -- 1953 1953 (completed 1916) 1929: The Universe is expanding ! Albert Einstein & Edwin Hubble Mt. Wilson 100-inch telescope (1931) Redshift (z) due to Expansion of the Universe Cosmological Redshift of Quasar Spectra z = 6.3 z = 4.4 z = 2.8 0.4 0.6 0.8 1.0 1.2 Wavelength (microns) Lyman Alpha emission of hydrogen 1216Å in rest frame TheThe distantdistant universeuniverse isis anan infraredinfrared universeuniverse Size ΩM = 0 of the Universe Open ΩM = 1 Closed -15 -10 -5 Today 510152025 Time (billions of years) The Decadal Review ranked Dark Dark Energy as the #1 Energy priority for NASA’s next major space Missions astronomy mission 2011 Nobel Prize in Physics Euclid dark energy mission • Euclid selected by ESA for 2019 launch ! • Teledyne’s H2RG IR detector and SIDECAR ASIC are baseline for the infrared instrument WFIRST – Wide Field Infrared Survey Telescope Eighteen 2K×2K arrays 75 Mpixel mosaic MaunaMauna Kea,Kea, HawaiHawai’iHawai’’ii TheThe NorthernNorthern HemisphereHemisphere’sHemisphere’’ss bestbest astronomicalastronomical sitesite Simplified AO system diagram Adaptive Optics Animation Imaging the galactic center Andrea Ghez University of California, Los Angeles Reinhard Genzel Max-Planck-Institut für extraterrestrische Physik Mass of black hole at center of the Milky Way = 4.1±0.6 million solar masses 2011 - 17 telescopes with 6.5-meter aperture or larger Hawai’i KeckKeck –– two two 10-m10-m LBTLBT –– twin twin 8.4-m8.4-m HETHET 9.2-m9.2-m (effective)(effective) GrantecanGrantecan 10.4-m10.4-m Canary Islands Subaru 8.2-m Texas Subaru 8.2-m GeminiGemini 8-m8-m MMTMMT 6.5-m6.5-m Arizona GeminiGemini 8-m8-m SALTSALT 10-m10-m (eff.)(eff.) Chile ESOESO VLTVLT –– four four 8.2-m8.2-m CarnegieCarnegie MagellanMagellan –– two two 6.5-m6.5-m South Africa The era of the Extremely Large Telescopes (ELTs) is imminent Giant Magellan Telescope Thirty Meter GMT Telescope 24.5-m TMT 359 m2 30-m European Extremely 707 m2 Large Telescope Existing Large E-ELT Telescopes 944 m2 of 39-m collecting area 1194 m2 3 6.5-m 9 8-m 5 10-m HgCdTeHgCdTe SensorsSensors forfor AstronomyAstronomy State-of-the-artState-of-the-art •• Large Large formatformat TeledyneTeledyne H2RGH2RG 2K×2K2K×2K –– 2048×2048 2048×2048 pixelspixels isis standardstandard –– 4096×4096 4096×4096 pixelspixels isis inin developmentdevelopment Raytheon VIRGO 2K×2K •• Quantum Quantum efficiencyefficiency Raytheon VIRGO 2K×2K –– 70-90% 70-90% overover widewide bandpass;bandpass; UVUV throughthrough infraredinfrared •Noise•Noise TeledyneTeledyne H4RG-15H4RG-15 4K×4K4K×4K –– Dark Dark currentcurrent cancan bebe mademade negligiblenegligible withwith coolingcooling –– Readout Readout noisenoise asas lowlow asas 2-32-3 electronselectrons withwith multiplemultiple samplingsampling –– Dynamic Dynamic rangerange (full(full wellwell // totaltotal noisnoise)e) ofof ~10,000~10,000 forfor thethe bestbest sensorssensors •• What What astronomersastronomers wantwant toto bebe improvedimproved inin HgCdTeHgCdTe sensorssensors –– Latency Latency // Persistence:Persistence: 0.1%0.1% degradesdegrades sciencescience –– Operability: Operability: 95% 95% toto 99%99% specsspecs setset byby costcost –– LWIR LWIR Producibility:Producibility: LWIR LWIR moremore difficult,difficult, withwith lowerlower yieldyield –– High High speed,speed, lowlow noise:noise: 500 500 HzHz frameframe rate,rate, 12812822,, 33 e-e- noise noise –– Cost: Cost: IR IR detectorsdetectors areare ~10×~10× visible visible CCDsCCDs FutureFuture AstronomyAstronomy DiscoveriesDiscoveries