Arsenic doping at concentrations CAs ≳ 1018 cm-3 during Si(001) growth from hydride precursors gives rise to strong As surface segregation, low film growth rates RSi, poor electrical activation, and surface roughening. Based upon the results of temperature-programmed desorption studies of Si(001):As surface processes during film deposition, we have investigated the use of temperature-modulated growth including periodic arsenic desorption (10 s at 1000 °C) from the surface segregated layer. Both constant-temperature and temperature-modulated Si(001):As layers were grown at Ts=750 °C, selected as a compromise between maximizing CAs and providing a usable deposition rate, by gas-source molecular beam epitaxy from Si2H6/AsH3 mixtures. For constant-temperature growth, RSi is only 0.08 μmh-1, the fraction of electrically active dopant is 55%, and film surfaces are very rough (rms roughness 〈w〉 = 110 A°). In sharp contrast, Ts-inodulated layers exhibit increases in RSi by 2.5× to 0.20 μm h-1, 100% electrical activity, and atomically smooth surfaces with 〈w〉 = 2 Å. The results are explained based upon the competition among As surface segregation, desorption, and incorporation rates.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)