TEMPERATURE-DEPENDENCE OF THE 0.7-2E(2) H QUASI-PLATEAU IN STRONGLY CONFINED QUANTUM POINT CONTACTS/

New results are presented of the ''0.7'' (2e(2)/h) quasi-plateau of st rongly confined point contacts. The strong confinement is obtained by combining shallow etching with metal gate deposition on GaAs/GaAlAs he terostructures. The resulting subband separations are up to 20 meV, an d consequently, the quantized conductance is observed up to 30 K, an o rder of magnitude higher than in conventional split gate devices. Pron ounced quasi-plateaus are observed at the lowest conductance steps fro m 1 to 30 K, where all structures are smeared out thermally. The devia tion of the conductance from ideal integer quantization exhibits an ac tivated behavior as a function of temperature with a density-dependent activation temperature around of 2 K. Our results are analyzed in ter ms of a model involving scattering against plasmons in the constrictio n. (C) 1998 Elsevier Science B.V. All rights reserved.