19 September 2016 Optimization of TCR and heat transport in group-IV multiple-quantum-well microbolometers
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Group-IV semiconductors have the opportunity to have an equivalent or better temperature coefficient of resistance (TCR) than other microbolometer thermistor materials. By using multiple-quantum-well (MQW) structures, their TCR values can be optimized due to a confinement of carriers. Through two approaches – an activation energy approximation and a custom Monte Carlo transfer matrix method – we simulated this effect for a combination of Group-IV semiconductors and their alloys (e.g., SiGe and GeSn) to find the highest possible TCR, while keeping in mind the critical thicknesses of such layers in a MQW epitaxial stack. We calculated the TCR for a critical-thickness-limited Ge0.8Sn0.2/Ge MQW device to be about -1.9 %/K. Although this TCR is lower than similar SiGe/Si MQW thermistors, GeSn offers possible advantages in terms of fabricating suspended devices with its interesting etch-stop properties shown in previous literature. Furthermore, using finite element modeling of heat transport, we looked at another key bolometer parameter: the thermal time constant. The dimensions of a suspended Ge microbolometer’s supporting legs were fine-tuned for a target response time of 5 ms, incorporating estimations for the size effects of the nanowire-like legs on thermal conductivity.
Conference Presentation
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Matthew Morea, Matthew Morea, Kevin Gu, Kevin Gu, Victoria Savikhin, Victoria Savikhin, Colleen S. Fenrich, Colleen S. Fenrich, Eric Pop, Eric Pop, James S. Harris, James S. Harris, "Optimization of TCR and heat transport in group-IV multiple-quantum-well microbolometers", Proc. SPIE 9974, Infrared Sensors, Devices, and Applications VI, 99740M (19 September 2016); doi: 10.1117/12.2236166; https://doi.org/10.1117/12.2236166

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