Epitaxial growth of GaN using reactive neutrals extracted from the nitrogen Helicon wave plasma

Abstract

A GaN epilayer on sapphire (0001) was grown using the N-2 Helicon wave plasma assisted evaporation deposition process. Various methods to reduce the N-2 ion impingement energy were attempted. The addition of inert gas (Ar, Ne) into the N-2 plasma decreased the impingement of N-2 ions and generated a higher quantity of activated nitrogen. In addition, the installation of mirror-type magnets effectively reduced the ion impingement energy. Although the ion impingement energy was less than the threshold (similar to 25 eV) for damaging GaN, the high flux of ion impingement during the growth of GaN induced a considerable strain in the epilayer. GaN film synthesized under direct ion impingement onto the growing surface has poor luminescent properties, despite its relatively good crystallinity. When the neutral nitrogen was utilized for GaN epilayer growth, the crystallinity and luminescent properties were greatly improved. Furthermore, with the decreasing of kinetic energy of fast neutral nitrogen, the in-plane crystallinity of GaN was improved and thus, an enhancement of luminescent properties was attained. (C) 2000 American Vacuum Society. [S0734-2101(00)01906-0].