Dependences of the Transport Scattering Time and Quantum Lifetime on the Two-Dimensional Electron Gas Density in Modulation-Doped Single GaAs Quantum Wells with AlAs/GaAs Short-Period Superlattice Barriers

Abstract

The dependences of the transport scattering time t, quantum lifetime q, and their ratio t/q on the density ne of the electron gas in modulation-doped single GaAs quantum wells with AlAs/GaAs short-period superlattice barriers are investigated. The experimental dependences are explained in terms of electron scattering by remote ionized donors with an effective two-dimensional concentration n*R and background impurities with a three-dimensional concentration nB. An expression for n*R(ne) is obtained including the contribution of X-valley electrons localized in AlAs layers to the suppression of scattering by the random potential of remote donors. It is shown that the experimentally observed abrupt increase in t and q with an increase in ne above a certain critical value nec is related to a decrease in n*R. It is established that the drop in t/q observed for electron densities ne > nec occurs because scattering by the random potential of background impurities in this two-dimensional system with a decrease in n*R limits an increase in t more considerably than an increase in q.

Suppression of Magneto-Intersubband Resistance Oscillations by Large-Scale Fluctuations of the Intersubband Energy Splitting

“…In particular, such structures contain large-scale fluctuations of the 2D electron gas density δn, which lead to the inhomogeneous broadening of Landau levels and are manifested in the nonlinearity of Dingle plots, i.e., dependences of the logarithm of the amplitude of Shubnikov-de Haas (SdH) oscillations on the inverse magnetic field [3]. The form of Dingle plots is determined by the temperature T and broadening mechanisms of Landau levels, and they are widely used to study the processes of scattering of the 2D electron gas in semiconductor heterostructures [5][6][7][8].…”

“…Such effect of V g on the behavior of is quite expectable. First of all, the negative gate voltage V g squeezes out X electrons localized in AlAs layers adjacent to the Si-δdoped layer located between the Schottky gate and the quantum well [8]. The decrease in the concentration of compact dipoles, which are formed by positively charged donors in the Si-δ-doped layer and X electrons in AlAs layers, increases the scattering of electrons on the random potential of the dopant, which suppresses MIS oscillations.…”