Boron surface segregation in Si molecular beam epitaxy has been measured on Si(111) substrate as a function of the growth temperature (400 °C≤T s≤900 °C) by Auger electron spectroscopy. Boron oxide (B 2O3) was used as dopant material to achieve a boron concentration level of about 1×1019 cm-3. Three temperature regions are observed for the behavior of the ratio r d=Is/Ib of the surface (Is) to the bulk (Ib) dopant atomic fractions. At low temperature, T s=400-570 °C the ratio maintains at the value r d≅1.5. For 570 °C≤Ts≤720 °C, r d increases to a plateau rd≅5.5, and then jumps to rd=42 in the 720-750 °C region. At higher temperature, T s≥750 °C, rd decreases according to a relation which can be approximated by the classical equilibrium segregation theory. In that region, the boron Gibbs free energy of surface segregation is calculated from data to be ΔGS=-0.33±0.02 eV. Evolution of r d is closely correlated to the etch pit count and electron channeling results revealing amorphous, polycrystalline, and epitaxial growth, when going from low to high growth temperature.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)