Low-temperature molecular beam epitaxy was used to grow B doping superlattices with peak B concentrations of 1018/cm3 and spike width of 10nm. Amorphization of the superlattices was achieved by using a series of 30 and 112keV Si+ implants; each to a dose of 1015/cm2. This placed the amorphous/crystalline interface between the first and second doping spikes. The dose rate of Si+ implantation was varied from 0.13 to 1.13mA/cm2. Post-implantation rapid thermal annealing was carried out at 800C, for times varying from 5 to 180s. Secondary ion mass spectrometry was used to monitor dopant diffusion after annealing. It was found that increasing the implantation dose rate appeared to increase the interstitial flux towards the surface, but had no observable effect upon the flux into the crystal. Transmission electron microscopy was used to study the end-of-range defect evolution. An increase in dose rate was observed to decrease the end-of-range defect density. The observations were consistent with previous findings that had indicated that the amount of back-flow towards the surface decreased as the end-of-range loop density increased.

L.S.Robertson, A.Lilak, M.E.Law, K.S.Jones, P.S.Kringhøj, L.M.Rubin, J.Jackson, D.S.Simons, P.Chi: Applied Physics Letters, 1997, 71[21], 3105-7