ELECTRON-TEMPERATURE AND THERMAL CONDUCTANCE OF GAAS 2D ELECTRON-GAS SAMPLES BELOW 0.5-K

The electron phase coherence length is used as a thermometer to measur e the temperature of a 2DEG. We find that the electron temperature dif fers from the mixing chamber temperature of the refrigerator by as muc h as 100 mK at base temperature. We also measure the thermal resistanc e between the electron gas and the mixing chamber and find a resistanc e comparable to that predicted by the Wiedemann-Franz law for the elec tron gas alone. Our results indicate an extraneous power level of abou t 4 pW in our experimental configuration.