Nitrogen plasma optimization for high-quality dilute nitrides

Growth of GaInNAs by molecular beam epitaxy (MBE) generally requires a nitrogen plasma, which complicates growth and can damage the wafer surface. Optical spectra from both ends of the plasma cell were nearly identical, and were found to be insensitive to certain changes in the cell condition evidenced by a change in reflected RF power and stability. A slight amount of excess capacitance in the matching network improved stability, particularly while the cell warmed up. Furthermore, despite steps to reduce the ion flux from the plasma, a remote Langmuir probe showed significant ions. Moderate voltages on deflection plates were sufficient to remove these ions, with a 3-5× increase in photoluminescence resulting from 18-40 V deflection.