Reactive sputtering of polyphosphide thin films by plasma cracking of P4

For the first time, we are reporting on the sputter deposition of amorphous-polyphosphide thin films from a compound target. We demonstrated that the growth rate of this compound semiconductor is determined by the metal flux, and the stoichiometry is determined by the phosphorus flux. The amount of excess phosphorus required to maintain the stoichiometry of the growing film was calculated. A new technique was used to provide the excess phosphorus, namely the generation of reactive phosphorus (P) species from P4 molecules injected into the plasma via an Ar carrier from an external P4 delivery system. The sticking coefficient of K is found to be independent of substrate temperature while that of the P species changes from 1 at 23 °C to 0.25 at 250 °C. The plasma-cracking efficiency is measured to be almost 100%. The effect of plasma on the P4 chemistry has implications for polyphosphide deposition and for the growth of other compound semiconductors containing Group V elements.