In this work, the optical and electrical properties of simultaneously grown modulation-doped heterostructures (MDH) on (100)- and (631)-oriented GaAs substrates are investigated. Due to the amphoteric behavior of Si in AlGaAs doped films two dimensional electron (2DEG) and hole gas (2DHG) structures for the growth on (100) and (631) planes, respectively are obtained. Atomic force microscopy (AFM) revealed atomically flat surface for the (100)-MDH sample. On the contrary, (631)-MDH sustained uniform corrugation along [1̄13] after the growth of the GaAs films, which provoked anisotropic mobility of the carriers at 77 K as confirmed by the Hall effect in a double arm bar. By photoluminescence spectroscopy (PL) the band to band transition, carbon and Si-related lines were identified. The concentration of the ternary alloy and impurities were evaluated by secondary ion mass spectrometry. © 2013 Elsevier B.V. All rights reserved.