B-doped Si(001)2 × 1 gas-source molecular-beam epitaxy from Si 2H 6 and B 2H 6

Abstract

The growth rates R Si, of Si films deposited on Si(001)2 × 1 from Si 2H 6 by gas-source molecular-beam epitaxy (GS-MBE) were determined as a function of temperature T s (500–950 °C) and impingement flux J Si 2H 6 (0.3–7.7 × 10 16 cm −2 s −1). R Si (T s, J Si 2H 6 ) curves were well described using a model, with no fitting parameters, based upon dissociative Si 2H 6 chemisorption followed by a series of surface decomposition reactions with the ratelimiting step being first-order hydrogen desorption from Si monohydride. The zero-coverage Si 2H 6 reactive sticking probability in the impingement-flux-limited growth regime was found to be 0.036. B doping concentrations (C B = 5 × 10 16 − 5 × 10 19 cm −3) from B 2H 6 increased linearly with increasing flux ratio J B 2H 6 /J Si 2H 6 at constant T s and decreased exponentially with 1/T s at constant J B 2H 6 /J Si 2H 6 . The B 2H 6 reactive sticking probability ranged from ≅ 6.4 × 10 −4 at T s = 600 °C to 1.4 × 10 −3 at 950 °C. Secondary ion mass spectrometry analyses of modulation-doped samples revealed sharp profiles with no detectable B segregation. Hole mobilities in uniformly-doped samples were equal to bulk values.