Temperature induced shift in the pinch-off voltage of mesoscopic devices

Detailed experimental studies of the conductance of mesoscopic GaAs devices in the few-mode regime reveal a novel thermal effect: for temperatures up to at least 10 K the measured gate characteristics, i.e. conductance $G$ versus gate voltage $V_g$, exhibit a systematic downward shift in gate voltage with increasing temperature. The effect is 'universal', in the sense that it is observed in different modulation doped GaAs/GaAlAs heterostructures, in different device geometries, and using different measurement setups. Our observations indicate that the effect originates in the surrounding 2D electron gas and not in the mesoscopic devices themselves.