Weak localization inAlxGa1−xAs/GaAs/AlxGa1−xAsheterostructures with electrostatically induced random antidot array

Abstract

main concern was with the investigations of the ballistic systems, in whichl > d, D, wherel is the mean free path, d andD are the size of antidots and period of the antidots array, respectively. The rich diversity of the transport phenomena, such as commensurable oscillations, the peculiarities due to the trajectories rolling along the array of antidots was observed. The antidots array structures in the diffusion regime (l < d,D) were not studied essentially. Such structures are interesting in some aspects. First of all, the quantum corrections to the conductivity due to weak localization (WL) and electron-electron (ee) interaction have to reveal the specific features when the phase breaking length, L� = p D��, where D is the diffusion coefficient and�� is phase breaking time, or the temperature length, LT = p D/T, become larger than d,D at decreasing temperature (hereafter we set kB = 1, ~ = 1). Secondly, the large enough negative gate voltage has to deplete the channels between the antidots (the channel widthw0 is aboutD−d) and as a result to lead to crossover to the hopping conductivity. Besides, from the transport properties standpoint the antidots arrays are the fine model of the granular media. In contrast to the granular metallic film, the parameters of the “granules” and “barriers” are reliably known and can be changed continuously within wide range. In this paper we report the results of the experimental study of the weak localization correction to the conductivity in the structure with the random array of antidots. We show that the change of the magnetoresistance at arising of the antidots and increase of the antidots size results from the change of statistics of closed paths. Namely, the contribution of the trajectories with the large enclosed area is strongly suppressed. The experimental area distribution function is in a reasonable agreement with the function obtained from the computer simulation. The random antidots array was made on the single quantum well heterostructure with the electron density n = 1.5 × 10 12 cm −2 and mobility µ = 19000 cm 2 /(Vs) δ - Si t 2 GaAs