TEMPERATURE LIMITS FOR BALLISTIC QUANTIZATION IN A GAAS/ALGAAS ONE-DIMENSIONAL CONSTRICTION

One-dimensional (Io) ballistic constrictions have been made in a two-dimensional electron gas of high carrier concentration (6.5 x 10(11) cm(-2)) and high mobility (9.5 x 10(5) cm(2) v(-1) s(-1)) formed at the interface of a GaAs/AlGaAs heterostructure. At least seven ballistic conductance steps were clearly observed at 4.2 K and remained discernible up to 40 K. A 1D subband spacing of 10 meV was found from the electric-field-induced half plateaux in differential conductance. The mobility and carrier concentration of the two-dimensional electron gas were also measured as functions of temperature in order to compare the relative effects on the degradation of the ballistic quantization of Fermi-Dirac broadening at the Fermi energy and the reduction in the ballistic mean free path. The close similarity between the experimental conductance characteristics and those calculated with a simple assumption of the Fermi-Dirac electron energy distribution strongly suggests that this is the principal mechanism in smearing the quantized conductance plateaux.