Distinguishing carriers' and lattice's temperatures through photoluminescence analysis

We report the direct and independent measurement of the lattice and the electrons temperatures in a nanocooler device (asymmetric double-barrier semiconductor heterostructure) at different operating points. Both temperatures are estimated from photoluminescence measurements - the former through the shift of the absorptivity profile, the latter through the shape of the blackbody baseline. The device's cooling feature results from the thermionic extraction of electrons injected in a quantum well through an energy selective barrier. While electrons exhibit a spectacular cooling for resonant injection, the lattice temperature remains essentially unaffected, with a temperature decrease at the resolution limit. Further from resonance, both systems show an identical thermal behavior governed by Joule's heating. The similarities and discrepancies of the temperature profiles illustrate the complex thermal behavior of the system, epitomize the need of reliable thermometry method and showcase the ability of photoluminescence to do so.