Electrical transport and far-infrared transmission in a quantum wire array

A wide set of data obtained on a two-dimensional electron gas submitted to a tunable lateral modulation, induced using a split-gate technique, is pres ented. Owing to a unique design of the sample, it has been possible to comb ine in a single experimental run, far-infrared transmission measurements an d electrical transport measurements in both directions parallel and perpend icular to the lateral modulation. The discussion of the results emphasizes the correspondence between various features observed in both types of measu rements. Based on these features, three regimes of modulation are clearly i dentified, namely the weak, intermediate and strong modulation regimes. Far -infrared transmission data show that each of these regimes is characterize d by plasmon modes with a distinctive behavior. These behaviors are analyze d further with the use of transport data, which allow to determine the elec tron concentration in the structure for every condition of gate voltage. In the weak modulation regime, a quantitative analysis shows that the collect ive mode energy is consistent with that of a classical 2D plasmon at q=2 pi /a (where a is the period of the split gate), using the average electron co ncentration under the gate as the relevant parameter. In the intermediate r egime, the collective modes are confined plasmons. The observation of "conf ined Bernstein modes" indicates that the bare confinement potential is nonp arabolic in this regime. In the strong modulation regime, the observation o f a far-infrared resonance energy which does not depend on the modulation a mplitude, while the effective 2D electron concentration (within each wire) varies with gate voltage, shows that the collective mode is a Kohn mode. (C ) 1998 American Vacuum Society. [S0734-211X(98)11806-1].