MICROSCOPIC BEHAVIOR OF SILICON IN SILICON DELTA-DOPED LAYER IN GAAS

Silicon delta-doped layers in GaAs have been studied using scanning tu nneling microscopy and scanning; tunneling spectroscopy on cleaved (11 0) surfaces. The samples were grown using molecular beam epitaxy with two growth temperatures: 480 and 580 degrees C. The concentration of t he delta-doped layer was 0.03 monolayer. We show that, as in the case of bulk doping, the silicon has an amphoteric character: both Si-Ga an d Si-As are observed at 480 degrees C and donors are formed before acc epters. At 580 degrees C, the spatial repartition of silicon evidences the segregation of silicon. (C) 1998 American Institute of Physics. [ S0003-6951(98)00119-3].