thanks to thermal imaging techniques, researchers at purdue university (west lafayette, ind.) are now using the same hydrodynamic transport model that is used in the study of fluid flow to describe heat transport in solid semiconductors.
purdue university researchers have visualized temperature changes produced by ultra-small heat sources, gold strips formed on top of the semiconductor indium gallium arsenide. (purdue university image/amirkoushyar ziabari, bjorn vermeersch)
according to an article on the university website, the researchers used full-field thermoreflectance thermal imaging to visualize temperature changes that were produced by gold strips on top of the semiconductor indium gallium arsenide. the study reveleaed vortices of phonons that had previously only been seen in fluid flows.
“the new findings have potentially important implications for ‘thermal crosstalk,’ in which multiple heat sources next to each other impact the overall temperature of the system, hindering performance,” the article explained.
researchers noted that as components continue to get smaller and component-density increases, thermal crosstalk becomes increasingly important. this work will give a better understanding of how vortices are generated on the edge of heat sources and about the thermal behavior of materials at the nanoscale.
“the governing law of heat conduction,” according to the article, “known as the fourier law or the heat-diffusion equation, does not accurately predict thermal transport for devices on the nanoscale. because the fourier diffusion equation doesn't explain the heat transport at those scales, this transport regime is called non-diffusive.”
it added, “the fourier theory substantially overestimates the experimentally observed temperature a short distance away from the heater lines.”
researchers found that within one or two microns of a small heat source that temperature could be as little as one-third or one-fourth of what the fourier theory predicts.
the research was recently published in nature communications. the abstract stated:
“understanding nanoscale thermal transport is of substantial importance for designing contemporary semiconductor technologies. heat removal from small sources is well established to be severely impeded compared to diffusive predictions due to the ballistic nature of the dominant heat carriers.
“experimental observations are commonly interpreted through a reduction of effective thermal conductivity, even though most measurements only probe a single aggregate thermal metric. here, we employ thermoreflectance thermal imaging to directly visualise the 2d temperature field produced by localised heat sources on ingaas with characteristic widths down to 100 nm.
“besides displaying effective thermal performance reductions up to 50% at the active junctions in agreement with prior studies, our steady-state thermal images reveal that, remarkably, 1–3 μm adjacent to submicron devices the crosstalk is actually reduced by up to fourfold.
“submicrosecond transient imaging additionally shows responses to be faster than conventionally predicted. a possible explanation based on hydrodynamic heat transport, and some open questions, are discussed.”