PLASMONS IN SPATIALLY NONUNIFORM MAGNETIC-FIELDS

A non-planar two-dimensional electron gas (2DEG) has been realised by using molecular beam epitaxy to grow a high mobility heterostructure o n a (1 0 0) n(+)-GaAs layer selectively etched to create a two-dimensi onal array of cavities through the n(+)-GaAs which are bounded by high er-index facets. Far-infrared (FIR) cyclotron resonance spectra show o ne absorption mode associated with an electron gas formed inside the c avities and confined in both lateral directions. Typical confinement e nergies of 23 cm(-1) and widths of 1000 nm are derived from the FIR sp ectra and magneto resistance measurements. A second mode occurs at a f requency lower than that measured for a planar 2DEG. Its origin is dis cussed in terms of magneto-plasmons excited across a non-planar region of the electron gas in a spatially non-uniform magnetic held. Combini ng this information with atomic force microscopy images provides a com prehensive picture of the nature of the lateral confinement in this st ructure. (C) 1998 Elsevier Science B.V. All rights reserved.