Electrical transport properties of GaAs structures with a pair of acceptor and donor impurity delta-doped layers are studied. Beryllium is used as an acceptor impurity, while Se or Si is used as a donor impurity. The Be and donor impurity delta-doped layers are separated from each other with a 1-nm-thick spacer layer, and Be and donor impurity concentrations are varied among samples. In the samples with the p-type conduction where the Be doping concentration is higher than the donor impurity doping concentration, a transition from thermally activated conduction to metallic conduction occurs at room temperature with the resistivity at the transition being close to the quantum unit of resistance (1)/(2)h/e(2). In the samples with the n-type conduction where the donor impurity concentration is higher than the Be doping concentration, no such transition is observed. The different transport properties between two groups of samples indicate that heavy holes in the Be delta-doped layer behave as a quasi-two-dimensional system at room temperature, while electrons in the donor impurity delta-doped layer can no longer be considered as a quasi-two-dimensional system at high temperatures due to significant spreading of their wave functions in the direction normal to the delta-doped layer. The temperature dependence of resistivity of p-type pair delta-doped samples with high Hall mobility exhibits a broad peak in the low-temperature range. (c) 2006 American Vacuum Society.