We have investigated the width dependence of Sb delta (&dgr;) doping layers grown by Si solid phase epitaxy (SPE) on the Sb surface reconstruction prior to Si deposition. Depending on the Sb adsorption conditions a 2×1 and a 2×nsurface reconstruction is observed. Measurements of crystal truncation rods and x‐ray standing waves show a drastically reduced interface roughness and a better crystal quality for &dgr; layers grown on Sb:Si(001)−2×nsubstrates in comparison to Sb:Si(001)‐2×1, which we attribute to reduced surface stress of the Sb:Si(001)‐2×nreconstruction. ©1996 American Institute of Physics.