Magnetophonon resonance in the confinement of an n-GaAs/AlGaAs-heterojunction, tuned to a quasi-one-dimensional quantum wire

We observed and investigated for the first time a successive tunable transition from a two-dimensional electron gas (2DEG) to a quasi-one-dimensional quantum wire by magnetophonon resonance (MPR), occurring in the transverse magnetoresistance. Two differently prepared samples have been measured up to a magnetic field of View the MathML source and at temperatures between T=141 and View the MathML source. In principle, each sample consists of a 2DEG channel, with dimensions of about View the MathML source. The 2D → 1D transition has been caused by an electrostatic lateral confinement, located in the 2DEG plane and driven by a gate voltage Vg. We observed pronounced MP oscillations over the whole range of the applied gate voltages and temperatures. The phenomenon of the MP oscillation shows an inversion of extrema with increasing Vg, but no shift of the minima to lower fields, as both predicted by different theoretical treatments. The MP electron effective mass for the 1DEG increases up to 15%, compared to the 2D case. It decreases with temperature, as known from nonparabolicity for a 2DEG in GaAs.