OPERATION OF A COMPACT ELECTRON-CYCLOTRON-RESONANCE SOURCE FOR THE GROWTH OF GALLIUM NITRIDE BY MOLECULAR-BEAM EPITAXY (ECR-MBE)

The operation of an ASTeX compact electron cyclotron resonance plasma source and its effect on the growth of GaN thin films by electron cyclotron resonance-molecular beam epitaxy has been investigated. The role a flow Limiting orifice plays in increasing plasma stability as well as reducing ion damage and impurities in resultant films has also been studied. Both optical emission spectroscopy as well as electrostatic (Langmuir) probe studies have been employed to elucidate the generation and transport of charged and neutral species. With the introduction of the flow orifice, a substantial decrease in ion induced damage as well as surface roughening in the films is observed. This can be accounted for in terms of a collisionally induced relaxation of the grad-B acceleration of charged species toward the substrate in plasma sources employing axial solenoidal fields.