We have grown Mn delta-doped GaAs layers by molecular beam epitaxy with various Mn sheet concentrations (theta(Mn)) defined in the monolayer (ML) unit. Structural analyses using cross-sectional transmission electron microscopy and secondary ion mass spectroscopy revealed that when theta(Mn) is below 1 ML, Mn dopants are abruptly confined within 2-3 ML without lattice dislocations and clusters, and also without diffusion and surface segregation. Characterizations on the thermal stability of the doping profiles showed that the profiles retained abruptness even at elevated growth temperature T-s = 400degreesC without diffusion and significant segregation. Strong surface segregation of Mn atoms, lattice dislocations, and MnAs clusters appeared when theta(Mn) exceeds 1 ML. The transport properties of Mn delta-doped GaAs layers without and with selectively p-type doping are also presented. (C) 2002 Elsevier Science B.V. All rights reserved.