Reduced activation temperature of B impurities in Si(001) epitaxial layers grown by sputter epitaxy using B-doped Si(001) target compared with Si(111) target

Abstract

We have investigated the effect of the crystallographic orientation of B-doped Si (p-Si) crystalline targets on the activation temperature of B dopants in Si epitaxial layers grown on Si(001) substrates by the sputter epitaxy method. Specifically, we compared p-Si targets with two different surface orientations, (001) and (111). We found that the activation temperature depended on the crystallographic orientation of the B-doped p-Si target and B impurities began to be activated at a growth temperature of 680 °C when using the p-Si(111) target and at 560 °C, which is 120 °C lower, when using the p-Si(001) target. This phenomenon is discussed in this paper in terms of the difference in the level of crystallographic plane matching between the growth and target surfaces and the associated energetic barrier to B-atom activation. The case of P-doped Si (n-Si) was also compared, which showed no indication of target crystallographic orientation dependence, when comparing n-Si(001) and n-Si(111) targets, and the P activation began at around 250 °C. These findings are considered associated with P being more easily incorporated into Si lattice than B. The hole Hall scattering factors and estimated drift mobilities obtained with the p-Si(111) target were comparable to previously reported values, whereas those obtained with the p-Si(001) target were 0.17 and 15–23 % lower, respectively, suggesting that the p-Si layers grown using the p-Si(001) target had slightly more defects, possibly owing to lower growth temperatures.