Supersonic jet epitaxy of III-nitride semiconductors

Abstract

In this review we report on the application of supersonic jets towards growth of the III-nitride semiconductors AlN, GaN, and InN. Certain properties of supersonic jets provide unique advantages for film growth. A seeded jet is able to accelerate precursors to kinetic energies which are one to two orders of magnitude higher than the average kinetic energies in a typical CVD environment, which has been shown to enhance precursor adsorption and thus growth rate. Indeed, dual seeded supersonic jets have been effectively employed to grow GaN and AlN from organometallic precursors and ammonia. Supersonic jets can also be coupled with excitation sources to provide highly reactive precursors for film growth. For example, a supersonic plasma jet has been developed to generate atomic nitrogen, and this source has been used together with an effusion cell for gallium delivery to produce epitaxial GaN films. The tightly focused jet exit stream generates a very high peak flux at the centerline which produced a film growth rate of 0.65 μm/h. However, deposition nonuniformity is quite dramatic due to this focusing and due to the point source nature of supersonic jets. Relatively few studies of III-nitride supersonic jet epitaxy have been reported, so further work is needed to evaluate the usefulness of this growth technique.