Doping of Silicon Crystals with Bi and other Volatile Elements by the Pedestal Growth Technique

Abstract

Monocrystalline, high purity FZ-Silicon doped with bismuth is a promising laser material for the not jet opened up THz- band. With pill-doping during the common FZ-process only a narrow axial part of the crystal could be doped at a sufficient level. Crystals with FZ-like purity and a longer, highly doped section were grown after the well known pedestal technique using a specially developed pill-doping method out from axial holes in the pedestal feed rod being caped by the molten zone. Also doping with lithium and magnesium was done In this way for the first time. The crystals had diameters of 15-20mm using slim 35mm feed rods. Therefore up-scaling of the growth process and, at least for Bi doping, a dislocation-free structure appear achievable.