An explanation of trap-limited self-interstitial diffusion and enhanced boron clustering in boron doped silicon superlattices

Boron doped crystalline superlattices grown by low-temperature molecular beam epitaxy have been used by Stolk et al. to study the diffusion of self-interstitials I in Si. After 40 keV Si+ ion implantation and subsequent annealing, stationary interstitial profiles are found at 670 °C for periods t ~1 h, demonstrating that the penetration depth of interstitials is limited by trapping at hitherto unidentified impurities. In addition, the high
interstitial supersaturation causes B de-activation in the near-surface region. We show that both these effects, the trap-limited interstitial diffusion and the enhanced B clustering, can be explained, if the transient de-activation of boron is modeled by the first-order reaction I + B_s ->B_i. Boron atomic and electrical profiles as well as self-interstitial profiles are computed which are in good agreement with the experimental results.