  We discuss the theory of cooling electrons in solid-state devices via
``evaporative emission.'' Our model is based on filtering electron subbands in
a quantum-wire device. When incident electrons in a higher-energy subband
scatter out of the initial electron distribution, the system equilibrates to a
different chemical potential and temperature than those of the incident
electron distribution. We show that this re-equilibration can cause
considerable cooling of the system. We discuss how the device geometry affects
the final electron temperatures, and consider factors relevant to possible
experiments. We demonstrate that one can therefore substantial electron cooling
due to quantum effects in a room-temperature device. The resulting cooled
electron population could be used for photo-detection of optical frequencies
corresponding to thermal energies near room temperature.
