Heavy Phosphorus Doping in Molecular Beam Epitaxial Grown Silicon and Silicon/Germanium with a Gap Decomposition Source

Abstract

ABSTRACTDonor-doping in silicon molecular beam epitaxy (MBE) is still an open problem, due to the low solid solubility and the strong segregation behavior (Sb, As) or to the high vapor pressure of the doping elements (P, As). Based on its high solubility elemental P2 would be the best candidate for heavy n-type doping. A new developed phosphorus source, based on the decomposition of solid GaP with a simultaneously mass separation of the parasitic Ga atoms has been applied. Homogenous P-doping higher than 1019 cm3 in Si and strained SiGe has been achieved. No surface accumulation of phosphorus was observed. The parasitic Ga incorporation is about three orders of magnitude below the P concentration. In this paper we will demonstrate the use of such cell to incorporate electrical active phosphorus during MBE growth. The incorporation probabilities into Si and strained SiGe will be compared. The dependence of segregation-/diffusion processes of phosphorus on growth temperature during the MBE will be shown. SIMS investigations on undoped Si layers reveal no P or Ga “memory effect” of the UHV equipment.