FAR-INFRARED STUDY OF A QUASI-ONE-DIMENSIONAL ELECTRON-GAS FORMED ON (100)GAAS WITH HOLE GAS SIDEGATES ON A (311)A GAAS SUBSTRATE

A new type of quasi-one-dimensional electron gas (Q1DEG) has been prod uced using molecular beam epitaxy to grow a high mobility heterostruct ure on a (311)A GaAs substrate selectively etched to expose (100) face ts. The electron gas on the (100) facets is confined in one dimension by the two-dimensional hole gases on the (311)A faces, forming a p-n-p structure. Fourier transform infrared (FTIR) cyclotron resonance (CR) measurements and magneto-resistance measurements have been made on th ese Q1DEGs for various biases (V-h) between the hole and electron gase s to investigate its effects on the confinement potential, the Q1DEG e ffective width and the areal carrier density N-s. In the presence of a magnetic field the FTIR spectra show a strong peak attributable to a confined magnetoplasmon excited parallel to the lateral confinement di rection. Weaker peaks occur at higher frequencies corresponding to har monics. For all the peaks the magnetoplasma frequency falls with decre asing V-h until a threshold is reached at which the trend changes dram atically and a new mode appears. This behaviour is discussed in terms of nonparabolicity of the confining potential. (C) 1998 Elsevier Scien ce B.V. All rights reserved.