1 / 58

Advancements in HgCdTe APD Technology for Astronomy Applications

Explore the latest developments in HgCdTe APD arrays for astronomy, highlighting superior performance in low noise, high sensitivity, and high-speed applications. Understand the advantages over conventional APDs like Si, Ge, and GaAs, and learn about the unique characteristics of electron (e-APD) and hole (h-APD) avalanche in HgCdTe material.

knaylor
Download Presentation

Advancements in HgCdTe APD Technology for Astronomy Applications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ELECTRON- AND HOLE- AVALANCHEHgCdTe PHOTODIODE ARRAYS FOR ASTRONOMYDonald N. B. HallInstitute for AstronomyUniversity of Hawaii

  2. OUTLINE • WHY APDs? • CONVENTIONAL APD’S e.g. Si, Ge & GaAs. • WHY Hg:Cd:Te – the PERFECT INFRARED (and VISIBLE) APD MATERIAL? • e-APD and h-APD CHARACTERISTICS of Hg:Cd:Te. • STATUS of the NASA FUNDED UH/GSFC/TELEDYNE Hg:Cd:Te APD PROGRAM. • UH TEST and CHARACTERIZATION. • FUTURE DEVELOPMENTS.

  3. WHY APDs? • THE HAWAII-2RG ARRAYS DEVELOPED FOR JAMES WEBB APPROACH THE IDEAL DETECTOR IN ALL BUT ONE RESPECT – READ NOISE! • DUE TO BASIC PHYSICS OF CMOS, READ NOISE HAS IMPROVED LITTLE SINCE HUBBLE NICMOS – TECHNOLOGY LARGELY FROZEN IN TIME FOR 20 YEARS. • READ NOISE LIMITS LOW BACKGROUND AND/OR HIGH SPEED APPLICATIONS • Hg:Cd:Te APDs HOLD PROMISE OF THE SOLUTION.

  4. EXAMPLES • HIGH SPEED – MODEST FORMAT, RELAXED DARK CURRENT: - Wave-front Sensing - Fringe Tracking • HIGH SENSITIVITY – LARGE FORMAT, DEMANDING DARK CURRENT: - High Resolution Spectroscopy - Low Background Space • BOTH – ALSO HIGH TIME RESOLUTION: - Time Resolved Spectroscopy - Quantum Astrophysics

  5. CONVENTIONAL APDs e.g. Si, Ge & GaAs • IN CONVENTIONAL APD MATERIALS (e.g. Si, Ge and GaAs) BOTH ELECTRONS AND HOLES AVALANCHE (IN OPPOSITE DIRECTIONS). • THIS SPREADS THE STATISTICAL AVALANCHE GAIN PRODUCING EXCESS NOISE. • McINTYRE (1968) DEFINED THE EXCESS NOISE FACTOR: F = (S / B)IN / (S / B)OUT • THE THEORETICAL LIMIT FOR “F” IN THE CASE WHERE BOTH ELECTRONS AND HOLES AVALANCHE IS 2 BUT IT IS OFTEN >>2. • THIS DUAL AVALANCHING ALSO SIGNIFICANTLY STRETCHES OUT RESPONSE TIME. • BEST CONVENTIONAL APDs REACH F VALUES ~ 2

  6. McINTYRE MODEL • PHOTO-IONIZATION INITIATES AVALANCHING BY BOTH ELECTRONS AND HOLES. • COLLISIONS FULLY REDISTRIBUTE BOTH ELECTRONS AND HOLES BEFORE REACHING IONIZING ENERGY. • EXCESS NOISE AND PULSE BLURRING INHERRENT IN PROCESS. • RULES OUT “NOISELESS” (F = 1) PHOTON COUNTING IN LINEAR MODE. • PHOTON COUNTING ONLY IN GEIGER MODE WITH LIMITED DUTY CYCLE, AFTER-PULSES AND REQUIREMENT FOR QUENCHING.

  7. Hg:Cd:Te AVALANCHE CHARACTERISTICS • IT IS WELL KNOWN THAT BY VARYING THE “x” FRACTION OF Hg(1-x):Cd(x):Te, THE CUT-OFF WAVELENGTH λc CAN BE VARIED OVER THE RANGE λc< 1.3 μm TO λc > 15 μm. • OVER THIS RANGE THERE ARE ALSO DRAMATIC CHANGES IN THE AVALANCHE PROPERTIES OF THE CRYSTAL LATTICE. • THE NEXT CHART SHOWS LOG10 GAIN vs BAND-GAP (eV) FOR LAYERS FROM LETI, BAE, TIS & DRS, ALL @ 77K & 6V REVERSE BIAS

  8. e- & h- APD REGIMES OF HgCdTe Figure5: The distinct e-APD and h-APD regimes of HgCdTe cross over at Eg ~ 0.65 eV (λco ~ 1.9 μm). At lower band-gaps the e-APD gain increases exponentially with decreasing bandgap - material for four manufacturers shows remarkably consistent results. To higher bandgap the ratio k = αh / αe asymptotically approaches pure h-APD at Eg = 0.938 eV – the ideal SAM layer.

  9. e-APD GAIN - SUMMARY T=200K

  10. AVALANCH PROPERTIES of HgCdTe • HOLE ACCELERATION IS VERY LOW – HIGH EFFECTIVE MASS – SLOWER. • e- ACCELERATION IS VERY HIGH - PHONON SCATTERING LOW – VERY FAST. • HOLE IONIZATION IS VERY LOW EXCEPT FOR 0.938 eV RESONANCE • e-IONIZATION IS VERY HIGH • THUS FOR EB < 0.6 eV (λC > 2μm) ONLY e- AVALANCHE (k = 0)

  11. HgCdTe as an e-APD • AVALANCHE GAIN INCREASES EXPONENTIALLY WITH BIAS & DECREASING EB. • e- TRAJECTORIES ARE BALLISTIC BETWEEN IONIZING COLLISIONS. • DETEMINISTIC SO NO EXCESS NOISE – F ~ 1. • VERY FAST PULSE - GAIN BANDWIDTH > 1THZ. • THERE IS NO GEIGER BREAKDOWN AND SO NO GEIGER MODE OPERATION. • HOWEVER NOISELESS (F ~ 1) PHOTON COUNTING IS POSSIBLE IN THE LINEAR (PROPORTIONAL) MODE TO GAIN ~ 104. • FOR ASTRONOMY, THE PRIMARY CHALLENGE IS TO REDUCE DARK CURRENT.

  12. APDs in MBE HgCdTe • DEPOSITION BY MBE ALLOWS A SEPARATE ABSORPTION-MULTIPLICATION (SAM) STRUCTURE. • A-LAYER GRADED INTO M-LAYER • TO AVOID PHOTOIONIZATION IN THE M-LAYER, λC FOR THE A-LAYER MUST BE LONGER THAN λC FOR THE M-LAYER. • MISMATCH IN CRYSTAL LATTICE PROPERTIES MAY LIMIT THE DIFFERENCE BETWEEN THE TWO λCs.

  13. BAND-GAP TRADE-OFF0.25 eV (λc ~ 4.5 μm) vs 0.5 eV (2.6 μm) • 0.25 eV M-LAYER HAS HIGH GAIN (>5,000 @ 12.5 V) WITH MATURE PROCESSING TECHNOLOGY. • BUT VERY SUSCEPTIBLE TO THERMAL BACKGROUND. • 0.5 eV M-LAYER HAS MUCH LOWER GAIN BUT OFFSET BY MUCH LOWER BACKGROUND. • 0.5 eV DARK CURRENT NOT DRAMATICALLY LOWER DUE TO TRAP INDUCED TUNNELING CURRENT. • OPTIMUM M-LAYER BANDGAP?

  14. J. ROTHMAN SUMMARY

  15. EMPIRICAL MODEL for e-APD GAIN • BECK (2001, 2002) DETERMINED THAT THE e-APD GAIN M VARIES WITH V AS: M = 2 (V – VTH)/(VTH/2) • VTH ~ 6.8 Eg FOR ALL COMPOSITIONS: 0.2 < x < 0.5 • “DEAD VOLTAGE” MODEL OF e-APD GAIN IN HgCdTe • FIGURE FOR VTH = 5 Eg AND ά = 1

  16. M KINCH_JEM_V37N9P1453_2008 page 1454 Fig. 2

  17. M KINCH_JEM_V37N9P1453_2008 page 1454 Fig.1.(a)

  18. M KINCH, EAPDs, page 122, Fig. 7.13

  19. e-APD DEVELOPMENT • DEFIR (Design and Future of the IR) INITIATIVE BRINGS TOGETHER SOFRADIR’S R&D WITH CEA-Leti. • MCT e-APD RESEARCH TOWARD INDUSTRIALIZATION. • PASSIVE AMPLIFIED IMAGING (PAI) & 3-D LADAR. • DRS DALLAS (WITH SELEX) - PAI & 3-D LADAR PLUS ASTRONOMY. • RAYTHEON - PAI & 3-D LADAR (PLUS ASTRONOMY?). • BAE R&D. • TIS – ASTRONOMY.

  20. e-APDs by CEA LETI, DRS, BAE & TIS

  21. e-APD ARCHITECTURE - DEFIR caption

  22. e-APD ARCHITECTURE - DSL caption

  23. THREE COMPLIMENTARY TIS APPROACHES

  24. e-APD GAIN - SUMMARY T=200K

  25. DEFIR F VALUES (J. ROTHMAN)

  26. e-APD GAIN σ - DRS caption

  27. e-APD GAIN σ - DRS caption

  28. e-APD GAIN σ - DEFIR caption

  29. e-APD GAIN (CUM) - DEFIR caption

  30. e-APD GAIN vs TEMP - SUMMARY

  31. e-APD GAIN vs TEMP - DEFIR caption

  32. e-APD GNDC - DEFIR caption

  33. e-APD GNDC vs TEMP - DEFIR caption

  34. e-APD PULSE PROFILE - DEFIR caption

  35. e-APD PULSE RISE TIME - DEFIR caption

  36. e-APD PULSE DECAY TIME - DEFIR

  37. h-APD APPLICATIONS TO ASTRONOMY • 0.938 eV (λc~ 1.32 μm) M-LAYER COMPATIBLE WITH A-LAYER INSENSITIVE TO ROOM TEMPERATUREBACKGROUND. • ATTRACTIVE FOR HST-LIKE MISSIONS & GROUND BASED APPLICATIONS. • SUBSTRATE REMOVAL FOR VISIBLE APPLICATIONS. • CHALLENGES ARE DARK CURRENT & ACHIEVING F ~ 1. • h-APD AVLANCHE PULSE ~ 10X SLOWER.

  38. h-APD DEVELOPMENT • RAYTHEON (RVS, HRL & RMS) HAS DEMONSTRATED SWIR (1.55 μm) e-APD BASED LADAR OPERATING AT 300K. • THEY REPORT NO EXCESS NOISE TO GAINS >100, NEP < 1nW & GHZ BANDWIDTH. • CZT => 6” Si WAFER PROCESSING.

  39. PERFORMANCE OF 90 RANDOMLY SELECTED APDs - RAYTHEON Jack et al, Proc of SPIE V6542, P65421A (2007)

  40. GOALS OF THE UH/GSFC/TELEDYNE Hg:Cd:Te APD PROGRAM • THREE YEAR PROGRAM FUNDED PRIMARILY BY NASA “RESEARCH OPPORTUNITIES IN SPACE AND EARTH SCIENCES” INITIATIVE - SUPPLEMENTAL FUNDING BY GSFC. • WILL UTILIZE TELEDYNE’S BROAD EXPERIENCE IN MBE Hg:Cd:Te PROCESSING TO PRODUCE APDs OPTIMIZED FOR ASTRONOMY. • UH WILL MODIFY TEST FACILITIES DEVELOPED FOR THE JWST PROGRAM TO CHARACTERIZE ARRAYS IN PHOTON COUNTING MODE.

  41. APPROACH • SIMILAR MASKS FOR e-APD & h-APD HgCdTe INCLUDE: - PROCESS EVALUATION CHIPS (PECs). - FOUR 256 x 256 @ 18 μm PITCH SUB-ARRAYS - TWO “TADPOLES” • SCREEN AND INITIAL EVALUATION OF LAYERS USING PECs. • CHARACTERIZE PHOTON COUNTING WITH SUB-ARRAYS BONDED TO CORNER OF H1RG, READ OUT WITH SIDECAR ASIC. • “TADPOLES” FOR HIGH SPEED (QUANTUM ASTROPHYSICS AND LADAR). • GOAL IS LOW DARK WITH F ~ 1.

  42. KSPEC MODIFICATIONS CONCEPTUAL “TADPOLE” LAYOUT Diodes in the 64um-500um range aligned along two parallel lines

  43. UH-TIS HAWAII Heritage HAWAII - 1 HAWAII - 2 HAWAII - 1R HAWAII - 1RG HAWAII - 2RG 1994 1998 2000 2001 2002 WFC 3 1024 x 1024 pixels 3.4 million FETs 0.8 µm CMOS 18 µm pixel size 2048 x 2048 pixels 13 million FETs 0.8 µm CMOS 18 µm pixel size 1024 x 1024 pixels 3.4 million FETs 0.5 µm CMOS 18 µm pixel size 1024 x 1024 pixels 7.5 million FETs 0.25 µm CMOS 18 µm pixel size 2048 x 2048 pixels 29 million FETs 0.25 µm CMOS 18 µm pixel size Guide mode & read/reset opt. Stitching On-chip butting Reference pixels Smaller pixels, Improved performance, Scalable resolution HAWAII-4RG-15 HAWAII-4RG-10 2011 (proposed) 2006 SIDECAR ASIC 15µm pixels 2003 4096 x 4096 110 million FETs 0.25 / 0.18 µm CMOS 15 µm pixel size 4096 x 4096 110 million FETs 0.25 µm CMOS 10 µm pixel size Control chip for H1RG, H2RG and H4RG-10/15

  44. DARK CURRENT vs TEMPERATURE FOR 2.5 AND 5 UM MATERIAL

  45. CURRENT STATUS • FIRST RUN OF n-on-p e-APDs HAD POOR DIODE CHARACTERISTICS. • ATTRIBUTED TO PROBLEMS WITH SURFACE PASSIVATION. • IN 2009 CONDUCTED AN EXTENSIVE INVESTIGATION OF SURFACE PASSIVATION. • READY TO PROCEED WITH 2ND RUN. • FIRST RUN OF p-on-n h-APDs UNDERWAY. • TESTING IN NOVEMBER. • EVALUATION OF h-APD GAIN of TIS HERITAGE 0.73 eV (λco ~ 1.7 μm) p-on-n PEC

  46. h-APD GAIN of TIS HERITAGE 0.73 eV (λco ~ 1.7 μm) p-on-n PEC • STANDARD 0.73 eV (λco ~ 1.7 μm) p-on-n PEC. • NO APD OPTIMIZATION OR SAM – ALL SAME MATERIAL. • GAIN & BANDGAP CONSISTENT WITH h-APD AVALANCHING. • PLAN TO EVALUATE IN H1RG. • PRESENT h-APD RUN CONSISTS OF THIS MATERIAL FOR A-LAYER WITH 0.938 eV M-LAYER.

  47. h-APD GAIN of TIS HERITAGE 0.73 eV (λco ~ 1.7 μm). p-on-n PEC Figure 3: Measured gain vs. reverse bias voltage for TIS heritage 0.73 eV p-on-n material (λco ~ 1.7 μm).

  48. KSPEC UPGRADE - CURRENT STATUS • COMPLETELY SEALED, ULTRA LOW BACKGROUND TEST FACILITY. • ILLUMINATION BY IR LEDs. • REFERENCE DETECTORS. • HIGH GEOMETRIC ATTENUATION TO < 1 PHOTON per PIXEL per FRAME READ • FIBER FEED OPTION FOR LASER PULSE MEASUREMENTS. • UP TO H2-RG. • <+ 1 mK TEMPERATURE CONTROL OVER 30K to 200K RANGE.

  49. KSPEC MODIFICATIONS Sphere Assembly Cryo ASIC Detector Module

  50. KSPEC X-SECTION LEDS APERATURE ASIC DETECTOR

More Related