Transport properties of AlAs/GaAs multilayer structures grown on (311)A GaAs substrates

In this paper we observe high-temperature anisotropic conductivity and mobility in orthogonal directions in the modulated Be-doped GaAs/AlAs superlattices grown on (311)A GaAs substrates. The ratio of the conductivities in the directions [<(2)over bar 33>] and [01(1) over bar] changes dramatically as the average GaAs layer thickness varied from structure to structure in the range from 4 to 500 Angstrom. The conductivity in the direction [01(1) over bar] is found to be essentially independent of temperature and GaAs layer thickness while the orthogonal one greatly increases with decreasing temperature and is structure dependent. The temperature behaviour of the hole gas concentration has an activated character. The activation energy has been found to increase with decreasing GaAs layer thickness.