Tunable, strongly non parabolic confinement in a quasi-one-dimensional electron gas formed by epitaxial regrowth

A new type of quasi-one-dimensional electron gas (Q1DEG) characterised by a tunable, strongly non parabolic confining potential in the lateral direction has been produced, using molecular beam epitaxy to grow a high-mobility heterostructure on a (311)A GaAs substrate selectively etched to expose (100) facets. The electron gas on the (100) facets is confined in one dimension by the two-dimensional hole gases on the (311)A facets, forming a p-n-p structure. Infrared cyclotron resonance (CR), magneto resistance and electron-beam-induced current (EBIC) measurements have been made on these Q1DEGs for various biases (V-h) between the hole and electron gases to investigate its effects on the confinement potential. Two different regimes are present. For V-h > -1.9 V, a strong peak attributable to a confined magnetoplasmon (CPM), together with its higher-frequency harmonics, are observed in the CR spectra. For V-h < -1.9 V, a new mode appears and the CPM no longer fits the experimental data. The anomalous dependence of the resonance frequency on carrier density, together with the EBIC images, provides some understanding of the tunable, non parabolic nature of the confining potential.