B-doped Si(001) grown by gas-source molecular-beam epitaxy from Si2H6 and B2H6:B incorporation and electrical properties

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Abstract
B‐doped Si(001)2×1 films were grown on Si(001) substrates by gas‐source molecular beam epitaxy using Si2H6 and B2H6. B concentrations CB (5×1016–5×1019 cm−3) were found to increase linearly with increasing flux ratio JB2H6/JSi2H6 (9.3×10−5–2.5×10−2) at constant film growth temperature Ts (600–950 °C) and to decrease exponentially with 1/Ts at constant JB2H6/JSi2H6 ratio. The B2H6 reactive sticking probability ranged from ≂6.4×10−4 at Ts=600 °C to 1.4×10−3 at 950 °C. The difference in the overall activation energies for B and Si incorporation at Ts=600–950 °C is ≂0.34 eV. A comparison of quantitative secondary‐ion mass spectrometry (SIMS) and temperature‐dependent Hall‐effect measurements showed that B was incorporated into substitutional electrically active sites over the entire B concentration range investigated. SIMS B depth profiles from modulation‐doped samples were abrupt with no indication of surface segregation to within the instrumental resolution limit and initial δ‐doping experiments were carried out. Structural analysis by in situ reflection high‐energy electron diffraction combined with post‐deposition 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. Temperature‐dependent (20–300 K) hole carrier mobilities were equal to the best reported bulk Si:B values and in good agreement with theoretical maximum values.