Atomic-scale study of GaMnAs/GaAs layers

Cross-sectional scanning tunneling microscopy was used to study GaMnAs diluted magnetic semiconductors grown by low temperature molecular beam epitaxy. The Ga1-xMnxAs layer, containing a concentration of x=0.005, shows that the dominant defect in the material is the arsenic antisite. Mn ions can also be resolved and show a signature distinct from the arsenic antisites. Spectroscopic measurements are perfomed to study the variation of the Fermi level between the Ga0.995Mn0.005As and GaAs layers. The Mn ions act as acceptor dopants. However, for x=0.005, the Mn concentration in comparison with the As antisite concentration is too small to induce a significant change of the Fermi level from the midgap position, preventing the layer from being ferromagnetic. (C) 2000 American Institute of Physics. [S0003-6951(00)03544-0].