Microscopic identification of dopant atoms in Mn-doped GaAs layers

Using cross-sectional scanning tunneling microscopy (XSTM), we have identified the dopant atoms in Mn-doped GaAs layers grown at 400 °C by molecular-beam epitaxy. The Mn-dopant atoms appeared as diffuse light areas superimposed on the background of As atomic rows in the STM images. The Mn acceptor concentration deduced from the STM images agreed well with the hole concentration determined by Hall measurements. No As antisite and associated defects were observed. These results indicate that Mn atoms are incorporated into the GaAs layer as electrically activated acceptors.