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Opportunities for IR Detector Development

29 th July 2005. Opportunities for IR Detector Development. Gavin Dalton Oxford Astrophysics / Rutherford Appleton Laboratory. Motivation Current Generation Detectors Cost drivers New opportunities Further Enhancements. Motivation. Much of ELT Science Case requires NIR

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Opportunities for IR Detector Development

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  1. 29th July 2005 Opportunities for IR Detector Development Gavin Dalton Oxford Astrophysics / Rutherford Appleton Laboratory Ringberg ELT Instrumentation

  2. Motivation • Current Generation Detectors • Cost drivers • New opportunities • Further Enhancements

  3. Motivation • Much of ELT Science Case requires NIR • High Spatial Resolution requires many pixels • Supply limited by volume, cost, politics etc • Small number of suppliers restricts technology development • Lifetime issues for hybridised arrays? • Instruments discussed this week already require few x 100 IR arrays – what about 2nd Gen.?  Detector costs for ELTs will exceed mirror costs?

  4. Motivation • EPICS – 50 arrays • MOMSI/MOMFIS – 24-150 arrays • NIRES - ~10 arrays • IRIS - ~100 • 2’ imager – few x 1000 (!!!)

  5. Historical Perspective • 4m instruments, hardware ~ 1M€ • 8m 1st gen: hardware ~ 2M€ • 8m 2nd gen: hardware ~ 5M€ • Detectors still a modest part of this (FMOS, KMOS, etc…) • Manpower costs more than hardware • VISTA IR: hardware ~ 10M€ • 4m instrument! • Hardware more than 2x manpower.

  6. VISTA-IR

  7. Current Detectors • Rockwell – PACE MBE • Raytheon – LPE • Both systems use hybridised arrays (detector wafer is bump-bonded to Silicon ROIC) • Enhancements possible in ROIC design (e.g. on chip DCS, readout ASICs etc)

  8. Current Detectors • Limitations & Cost Drivers: • Fundamental size limitations for CdTe wafers • Wafers are expensive • Bump bonding is difficult and expensive • Actual manufacture cost of a single detector is several FTEs • Detectors beginning to exhibit ‘lifetime’ effects • Closed market actually limits development • Still some issues for fast systems (detector flatness hard to control)

  9. New Opportunities • Potential new supplier (Qinetiq) identified through OPTICON KTN • Demonstration of direct growth of HgCdTe on to Si substrates (Hall et al, SPIE 5406, 317) • Fabricated 1024x1024 5µm array with Si substrate detector hybridised to Si ROIC. • Demonstration of wafer performance. • NB – Don’t know astronomical performance figures for these devices yet (RON, persistence, Dark Current etc…)

  10. Next Step • Direct growth of HgCdTe onto Si ROIC has been achieved, prototype arrays should now be in test. –bump bonding may be a thing of the past. • Many different levels of readout circuitry can be designed into the ROICs • Detectors built up from 240x320 pixel unit cells • Detectors not tuned to astronomical requirements. • Pixel size & filling factor • Wavelength range (doping) • Detector format – in principle could move to 12” Si wafers

  11. Further enhancements • Possibility of multi-layer detectors with layers tuned to different wavelength ranges (some trade-off with filling factors) • MCT sensitive out to 28µm, so opportunities for large format MIR arrays • Easier development testbed to work with than hybridised arrays  better route to develop IR WFS devices

  12. How to do it? • Preliminary R&D proposal (100k€) to PPARC for pixel design phase as lead-in to large-scale ELT Technology (6M€) Development package…both unfunded  • Now investigating alternative funding routes (possibility of collaborative broad sweep program with Synchrotron community [biosciences]). • Likely development programme could produce a new large-format science array within 5 years. - need to start soon! • May be able to reduce costs/risk with in-house ROIC development at RAL

  13. Prospects: • ELT detector complement (GMT, TMT, ELT) likely to exceed $250M with current technology. • European supplier for high cost items would be more palatable to EU funding agencies

  14. Prospects: • ELT detector complement (GMT, TMT, ELT) likely to exceed $250M with current technology. • European supplier for high cost items would be more palatable to EU funding agencies • $8-10M R&D could open a new opportunity: • At worst this would create a third supplier, enhanced competition, and minor cost reductions, but would probably recover the initial investment. • At best could envisage next generation arrays at fractional cost… could save $1-200M from programme costs.

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