Boron source for silicon molecular beam epitaxy

摘要

A simple effective and fairly stable boron source that is easy to prepare and simple to operate under UHV processing conditions is disclosed. The method for fabricating this boron source includes the in situ alloying of boron into a high melting point elemental semiconductor material, preferably silicon, in the hearth of an electron beam evaporator. A supersaturated solution of boron in silicon is created by melting the silicon and dissolving the boron into it and quenching the solution. The boron needs to be of high purity and may be in the form of crystalline granules for this to take place under controlled conditions and moderate power levels. When silicon is evaporated from this resultant silicon-boron alloy source, the silicon evaporates uncontaminated from a molten pool of the alloy in the center of the hearth. A segregation of boron into the liquid phase occurs and a segregation takes place from this molten phase into the vapor phase that is being evaporated from the pool. The boron incorporates without complex kinetics into the growing layers such as Si, Ge, Si-Ge alloys and metals as a dopant.