B INCORPORATION IN GE(001) GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY FROM GE2H6 AND B2H6

Secondary-ion-mass spectrometry (SIMS) was used to determine the concentration and depth distribution of B incorporated into Ge(001)2X1 films grown on Ge(001) substrates by gas-source molecular-beam epitaxy using Ge2H6 and B2H6. B concentrations C-B (3X10(16)-4X10(19) cm(-3) found to increase linearly with increasing flux ratio J(B2H6)/J(Ge2H6) (8.2X10(-3)-1.7) at constant film growth temperature T-s (300-400 degrees C) and to increase exponentially with 1/T-s at constant J(B2H6)/J(Ge2H6) ratio. The difference in the overall activation energies for B and Ge incorporation over this growth temperature range is congruent to 0.22 eV while B2H6 reactive sticking probabilities ranged from 8X10(-4) at 300 degrees C to 2X10(-5) at 400 degrees C. SIMS depth profiles from B modulation-doped samples and two-dimensional delta-doped samples grown at T-s<350 degrees C were abrupt to within instrumental resolution with no indication of surface segregation. Structural analysis by in situ reflection high-energy electron diffraction combined with postdeposition high-resolution plan-view and cross-sectional transmission electron microscopy showed that all films were high-quality single crystals with no evidence of dislocations or other extended defects. B doping had no measurable affect on Ge deposition rates. (C) 1995 American Institute of Physics.