High-frequency conductivity of ion-beam-defined quantum wires with a self-aligned gate

Abstract

Quasi one-dimensional quantum wire arrays are fabricated by low-energy ion beam exposure of AIGaAsGaAs heterostructures containing a high-mobility two-dimensha1 electron system (ZDES). The mask used for the ion beam exposure consists of a metal grating evaporated on the crystal surface, which also serves as a gate after irradiation. This self-aligned gate allows us to change the electron density in the wires without changing the electronic wire width. The linewidths of the dimensional resonances in the far infrared (FIR) of these wire arrays confirm this assertion. The FIR transmission spectra are compared with previous results obtained using wire arrays that were density tuned with a distance-modulated gate. Furthermore, a higher-order resonance is observable, indicating that the confinement potential has non-parabolic contributions.

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

“…Related observations have been reported a few times. 38,39,45,46,48,57 However, neither of these reports show the crossover between the intermediate and strong confinement regimes, which is clearly revealed in our results. Figure 11 shows a series of absorption spectra obtained at low pho- ton energy ͑ϭ254 m͒, where a multimode pattern appears when V g2 рV g рV g1 .…”

“…Another way to probe the electron gas is through optical measurements. A number of reports have been devoted to the probing of quasi-2DEG and quasi-1DEG energy spectrum using different techniques such as Fourier transform infrared spectroscopy ͑FTIR͒, [36][37][38][39][40][41][42][43][44][45][46][47][48] Raman scattering spectroscopy, [49][50][51][52][53][54][55][56][57] far-infrared ͑FIR͒ laser spectroscopy [58][59][60] and photoluminescence. [61][62][63][64][65][66][67][68][69][70] In all these techniques a collective excitation of the 1DEG is measured, the Raman scattering also giving information about single particle excitations.…”

Bernstein modes in a laterally modulated two-dimensional electron gas

“…In other cases, the 2DEG concentration itself was spatially modulated [8][9][10][11][12][13]. The spectra of the transmitted light were obtained using techniques based on far-infrared (FIR) Fourier spectroscopy [1,4,6,7,[9][10][11]13] FIR laser [8] or Raman spectroscopy [5,12]. Splitting of the magnetoplasmon mode was clearly seen in the neighbourhood of the n = 2 CR harmonic, and indications for a similar behaviour at n = 3 were obtained in a few cases [4,5,7,10].…”

“…In some of these experiments, samples were submitted to spatially modulated illumination (using a grating coupler) [1,[4][5][6][7]. In other cases, the 2DEG concentration itself was spatially modulated [8][9][10][11][12][13]. The spectra of the transmitted light were obtained using techniques based on far-infrared (FIR) Fourier spectroscopy [1,4,6,7,[9][10][11]13] FIR laser [8] or Raman spectroscopy [5,12].…”