Optical measurements of temperature in a quasi-two-dimensional exciton system

We have used time-resolved photoluminescence spectroscopy to measure the temperature of a gas of quasi-two-dimensional excitons. The exciton gas consists of both spatially direct and spatially indirect excitons in a coupled GaAs/AlxGa1-xAs double-quantum-well system. We show by experiment and modeling that the ratio of the intensities of the recombination radiation constitutes a sensitive, calibrated thermometer for the electron system. The technique is insensitive to inhomogeneous effects such as well-width fluctuations and is feasible at temperatures as low as several K.