Design optimization of Pixel Structure for α-Si based uncooled Infrared detector

  • Sudha Gupta Solid State Physics Laboratory, Delhi
  • Anupriya Katiyar Solid State Physics Laboratory, Delhi
  • R. K. Bhan Solid State Physics Laboratory, Delhi
  • R. Muralidharan Solid State Physics Laboratory, Delhi
Keywords: Uncooled infrared detector, microbolometer, thermal conductance


In this paper authors present the design and simulation results achieved for pixel structure of amorphous Si (α-Si) based bolometer array. Most uncooled IR detectors in the world are based on VOx material. But this is not a standard material in IC technology and has many inherent disadvantages. The α-Si, an alternative material with high TCR is becoming as popular. However, large TCR values, in this material are achieved only in films of high resistivity. To achieve TCR value more than 2.5%/K, α-Si film resistivity is ~ 80 ohms-cm. This gives rise to very large pixel resistance of the order of 100 Mega ohms depending upon the design of the leg structure. This high pixel resistance causes very large noise and hence lower sensitivity. If leg width or membrane thickness is increased in order to reduce the pixel resistance, then this results in higher thermal conductance which also decreases sensitivity. To overcome this problem, pixel structure is so designed that within a pixel, only part of the electrical conduction is through α-Si and rest is through metal. Simulation using Coventorware software has been done to optimize pixel resistance as well as thermal conductance through legs so that maximum sensitivity could be obtained. Optimization is also carried out in order to reduce sensitivity of pixel resistance to variation in material resistivity.

Defence Science Journal, 2013, 63(6), pp.581-588DOI:

Author Biographies

Sudha Gupta, Solid State Physics Laboratory, Delhi
Ms Sudha Gupta received her MSc (Physics) from the University of Delhi, Delhi, in 1986. She joined Solid State Physics Laboratory, Delhi, in 1987 and worked on the development of cooled IR detectors and focal plane arrays. Presently she is working on un-cooled thermal detectors. She has authored or coauthored more than 25 research papers in national and international journals/conferences.
Anupriya Katiyar, Solid State Physics Laboratory, Delhi
Ms Anupriya Katiyar has completed BTech  (Electronics and communication Engg) in 2008 from MMM Engg. College, Gorakhpur. Presently she is working as Scientist ‘B’ Solid State Physics Laboratory, Delhi. Her research area includes: design of amorphous-Si based microbolometer and photolithography for MEMS based  Microbolometer ,RF MEMS switch and microaccelerometer.
R. K. Bhan, Solid State Physics Laboratory, Delhi
Dr R.K. Bhan received his MSc (Physics) from Kashmir University, Srinagar, in 1982 and PhD (Physics) from Delhi University in 1994. Presently he is working as Scientist at Solid State Physics Laboratory, Delhi where he is involved in Infrared Detector characterization and MEMS devices. His research interests include MOS physics, CCDs, IR detectors and FPAs. He has published more than 60 research papers in international journals.
R. Muralidharan, Solid State Physics Laboratory, Delhi
Dr R. Muralidharan obtained his MSc (Physics) in 1975 from Madras and PhD from IISc, Bangalore in 1985. Presently working as Director of Solid State Physics Laboratory (SSPL), Delhi. His main area of work is MBE growth and characterisation of epitaxial layers for high electron mobility transistors and quantum dot devices. He is the recipient of -MRSI Medal 1989, Science Day Award-2003, and Technology Group Award of DRDO for Advancement in Material Growth using MBE
How to Cite
Gupta, S., Katiyar, A., Bhan, R., & Muralidharan, R. (2013). Design optimization of Pixel Structure for α-Si based uncooled Infrared detector. Defence Science Journal, 63(6), 581-588.