SURFACE SEGREGATION AND STRUCTURE OF SB-DOPED SI(100) FILMS GROWN AT LOW-TEMPERATURE BY MOLECULAR-BEAM EPITAXY

Sb surface segregation and doping during Si(100) molecular beam epitaxy were studied for growth temperatures of 320-500 degrees C. Surface segregation was analyzed by depth profiling with secondary ion mass spectrometry and the results indicate the existence of several distinct dopant concentration- and temperature-dependent surface segregation regimes: (1) For dilute Sb surface concentrations the measurements reveal a region where bulk and surface concentrations are linearly related, and the surface segregation is described by a constant. However, the experimentally determined temperature dependence of the segregation does not follow simple kinetics theory, and appreciable surface segregation is observed at temperatures less than or equal to 400 degrees C. (2) At temperatures >350 degrees C, the surface segregation reaches a maximum for Sb surface concentrations of 0.5 monolayers. (3) For surface concentrations near 1 monolayer, the surface segregation decreases with increasing surface Sb coverage due to dopant interaction within surface and subsurface layers. In cases where films were grown under very high dopant fluxes, we have identified cone-like defects and stacking faults that are the result of the apparent surface concentration exceeding 1 monolayer.