Digital infrared detectors
The University of Edinburgh in conjunction with Leonardo MW Ltd
The post will be based at the University of Edinburgh, but at the same time will provide the opportunity for close working with a team at Leonardo MW Ltd in Southampton in the context of carrying out IC Design and laboratory evaluation activities in the industrial environment.
“Digital infrared detectors”
Infrared sensor arrays are important for a wide variety of scientific, medical, security and military applications. Short wave infrared (900nm-2300nm) can make use of low levels of ambient light in the sky at night, medium wave (3-5micron) wavelengths are useful for imaging purely using thermal radiation through an atmospheric window in this waveband. Longer wavelengths (around 8-10 microns) are capable of great sensitivity owing to the peak in black body emissions at 300K being around this wavelength. All these wavelengths and also longer (10-16 microns) are used for measuring absorptions by various gases in the atmosphere and are used for scientific, astronomy and meteorological applications both ground and satellite based. The most sensitive arrays are today made with Mercury Cadmium Telluride (MCT) which can conveniently be tuned across this whole range of wavelengths. MCT is a typical IR detector material but others can be used.
In current 3rd generation IR detectors the signal generated by MCT photodiodes is captured by an analogue pixel circuit and processed using a readout integrated circuit (ROIC) implemented in CMOS technology. Current state-of-the art are passive staring 2D arrays and active gated (SPAD) arrays used with lasers. There are performance limitations with both these operating modes. MCT can achieve high gain linear mode APD operation. To exploit this material (along with other IR materials) a new ROIC architecture is required. This research is to work with Leonardo to capture the ROIC features that can produce a step change in sensitivity and performance for next generation IR detectors.
Initial areas of investigation should focus on in-pixel digitisation for time of flight and photon counting applications, not precluding 2D staring applications. The research should consider the possible exploitation of digital pixel circuits as a reconfigurable interface to MCT photodiode arrays for the next generation of IR detectors. Within this research programme it is expected that CMOS ICs will be designed and manufactured through a CMOS foundry prototyping service to facilitate laboratory evaluation.
Proposal for initial work:
- Analysis of requirements
- Literature study and state of the art review
- Develop candidates for concept review
This should be followed by a body of work to design and layout test structures to allow assessment of digital ROICs via a foundry prototyping service. The ultimate goal for Leonardo is the manufacture and hybridisation of digital IR focal plane arrays (DFPA) suitable for imaging trials.
Please contact Robert.Henderson@ed.ac.uk if interested.
Professor Robert Henderson
Minimum entry qualification - an Honours degree at 2:1 or above (or International equivalent) in a relevant science or engineering discipline, possibly supported by an MSc Degree. Further information on English language requirements for EU/Overseas applicants.