Secondary-ion mass spectrometry on δ-doped GaAs grown by molecular beam epitaxy

Improved resolution of secondary-ion mass spectrometry (SIMS) is obtained on Be δ-doped GaAs grown by molecular beam epitaxy at a temperature of 500 °C. The measured impurity distribution width is 29 Å, which corresponds to a SIMS resolution of ΔzR=25 Å. Impurity diffusion lengths of ≤10 Å can be detected by the technique. The surface segregation of Si impurities in δ-doped GaAs grown at 660 °C is investigated as a function of doping density. The segregation length increases with the Si density and is consistent with a segregation model based on the pinning of the Fermi level at the growing GaAs surface.