Practical aspects of solid source molecular beam epitaxial growth of phosphorus-containing films

The growth of phosphide films by solid source molecular beam epitaxy presen ts challenges in regard to safety, oxygen contamination, and disposal of re sidual phosphorus. Upon venting the growth chamber after phosphide growth, phosphine concentrations greater than the permissible exposure limit were m easured inside the chamber due to the reaction of moisture with residual re d phosphorus deposits on the chamber walls. Another product of the reaction is hydrated phosphorus oxides that can degrade subsequently grown aluminum -containing films. Procedures were developed to safely vent the growth cham ber as well as to minimize oxygen contamination of phosphide and arsenide f ilms. Contamination in the phosphide films was also caused by significant c oncentrations of oxygen in the bulk of the starting phosphorus ingot. The c ontamination was greatly reduced by lowering the phosphorus cracker tempera ture. A mechanism involving volatile phosphorus trioxide, P4O6, is proposed to qualitatively explain the effect of cracker temperature on oxygen conta mination. Due to incomplete cracking of sublimed elemental phosphorus, depo sits of flammable white phosphorus were created in the chamber. Procedures were developed to safely remove the white phosphorus from the machine and c onvert it into a nontoxic form for easy disposal. (C) 1999 American Vacuum Society. [S0734-211X(99)03405-8].