Characterization of a two-dimensional electron gas in GaAs–AlGaAs by surface acoustic waves

Abstract

We report simultaneous magnetotransport and surface acoustic-wave attenuation measurements performed at 1.25 K on a two-dimensional electron gas (2-DEG) GaAs-A1GaAs heterojunction sample. The carrier density was varied by means of the persistent photoconductivity effect. A comparison of the conductivity deduced from the two types of measurements is used to obtain information about the homogeneity of the 2-DEG sample. For this specific sample a simple model shows that there exists a 20% variation in the canier density at some intermediate carrier densities, while prior to illumination and after saturation with light the spread in carrier density in the sample was only a few percent.Nous presentons des mesures simultanees de magnetotransport et d'attknuation d'ondes acoustiques de surface effectuees a 1,25 K sur un Cchantillon d'hCtCrojunction 2-DEG (two-dimensional electron gas) GaAs-AIGaAs. Le densit6 des porteurs Ctait variee au moyen de I'effet de phtoconductivitC persistante. Une comparaison entre les valeurs de la conductivite deduites des deux types de mesures est utilisCe pour obtenir de I'information sur I'homogentite de I'echantillon. Dans le cas de cet Cchantillon particulier, un modele simple montre qu'il existe une variation de 20% dans la densite de,porteurs pour certaines densites intermediaires, alors qu'avant I'illumination et apres saturation lumineuse, les Ccarts entre les valeurs de la densite de porteurs dans I'Cchantillon n'itaient que quelques pour-cent.[Traduit par la redaction]Can.

Interaction of surface acoustic waves with a two-dimensional electron gas in the presence of spin splitting of the Landau bands

“…The emergence of these peaks is associated with spin splitting of the Landau zones, because for samples AG49 and BP92 their magnetic field positions correspond to occupation numbers ν = 3 and ν = 5, whereas for sample AG106 they correspond to ν = 1, where ν = nch/eH, c is the speed of light, h is Planck's constant, and e is the electron charge. We are convinced that the SAW absorption peak in a magnetic field corresponding to spin splitting of the Landau level has been observed in [11], but was not identified by the authors.…”

Elastic scattering and absorption of surface acoustic waves by a quantum dot

“…In order to apply Eq. (15), the relation between the bare SAW field and the screened potential V , to the diffusive dot under consideration, we consider its representation in terms of the diffusion modes defined in Eq. (20).…”

“…From an experimental point of view, these conditions are satisfied in a dot of size L ≃ 1 µm, patterened in an electron gas with a low mobility (µ ≃ 10 4 cm 2 /Vs) corresponding to l ≃ 100 nm. So, except for the shortest SAW's used in recent experiments, [12][13][14][15]10,16 ql is indeed small. This paper is organized in the following way.…”

“…Indeed, the SAW technique has been used successfully to investigate both the integer and the fractional quantum Hall regime. [11][12][13][14][15] These experiments have shown, e.g., that the SAW technique is suited to resolve very small spatial inhomogeneities in the areal electron density which are not visible in dc magnetoresistance measurements. 12,15 Effects of electron heating due to the electric field accompanying the SAW have been discussed in Refs.…”