Quantum and Transport Mobilities of Electrons in GaAs/Ga1?xAlxAs Multiple Quantum Wells

Abstract

The quantum and transport mobilities of electrons in modulation‐doped GaAs/Ga1−xAlxAs multiple quantum wells with well widths in the range between 51 and 145 Å and carrier density of about 1×1016 m−;2 have been investigated by magnetotransport measurements. The magnetic field dependence of the amplitude of the quantum oscillations in both magnetoresistance and Hall resistance have been used to determine the quantum (τq) and transport (τt) lifetimes (and hence the quantum (μq) and transport (μt) mobilities) of 2D electrons. The values thus found for μt are substantially smaller than those of the Hall mobility (μH) as obtained in the ohmic regime at low magnetic fields. The discrepancy between μt and μH has been explained in terms of a transport lifetime τt that depends on the electron energy due to the scattering of electrons by interface roughness in the quantum wells.

Determination of the In-Plane Effective Mass and Quantum Lifetime of 2D Electrons in Modulation-Doped In0.53Ga0.47As/In0.52Al0.48As Heterojunctions from the Quantum Oscillations in Hall Resistance

“…The straight lines in the figure represent the least-squares fits of Eq. (8) to each set of the experimental data. The slope (--pm * /et q ) of the straight line together with the measured values of m * have been used to determine t q ( Table 1).…”

“…For each sample studied, the periods of the quantum oscilations in DR xy (B) are found to be identical to those of the SdH oscillations in R xx (B). However, the amplitude of the Hall oscillations is about an order of magnitude smaller than that of the SdH oscillations in magnetoresistance (see also [8]). The Hall oscillations similar to those given in Figs.…”

“…Coleridge et al [1,5,6] pointed out that the validity of the semi-classical treatment leading to Eqs. (4) and (5) extends into the intermediate magnetic-field regime where w c t q < 2 and that there is no restriction on the value of w c t t as long as Dr xx < r 0 (see also [7,8]). In the case of a 2D electron gas where more than one subbands are populated, the quantum oscillations in magnetoresistance and Hall resistance can be represented by weighted sum of contributions from all populated subbands.…”

“…In the case of a 2D electron gas where more than one subbands are populated, the quantum oscillations in magnetoresistance and Hall resistance can be represented by weighted sum of contributions from all populated subbands. The Shubnikov-de Haas (SdH) oscillations in magnetoresistance have been extensively employed in the investigations of the electronic transport properties of highlydegenerate 2D structures at low temperatures (see for instance [1][2][3][5][6][7][8][9][10][11][12]). However, the measurements of quantum oscillations in Hall resistance (hereinafter named Hall oscillations) have not yet been used in the characterization of a multi-channel system such as a 2D electron gas with double-subband occupancy.…”

On the Role of Magnetic Field Fluctuations in Diffusive Shock Acceleration

“…This is, in turn, fixed by confining sources. It was indicated [2][3][4][5][6][7][8][9][10][11] that roughness-related scattering dominates transport in many heterostructures, especially thin square QWs. This is determined by the wave function near the interface.…”