American Institute of Physics, Applied Physics Letters, 2(107), p. 022104, 2015
DOI: 10.1063/1.4926338
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This is the author accepted manuscript. The final version is available from AIP via http://dx.doi.org/10.1063/1.4926338 ; We present measurements of the energy relaxation length scale l in two-dimensional electron gases (2DEGs). A temperature gradient is established in the 2DEG by means of a heating current, and then the elevated electron temperature Te is estimated by measuring the resultant thermovoltage signal across a pair of deferentially biased bar-gates. We adapt a model by Rojek and K?nig [Phys. Rev. B 90, 115403 (2014)] to analyse the thermovoltage signal and as a result extract l, Te, and the power-law exponent ?i for inelastic scattering events in the 2DEG. We show that in high-mobility 2DEGs, l can attain macroscopic values of several hundred microns, but decreases rapidly as the carrier density n is decreased. Our work demonstrates a versatile low-temperature thermometry scheme, and the results provide important insights into heat transport mechanisms in low-dimensional systems and nanostructures. These insights will be vital for practical design considerations of future nanoelectronic circuits. ; We acknowledge funding from the Leverhulme Trust, UK and the Engineering and Physical Sciences Research Council (EPSRC), UK.