Construction, Characterization, and Use of an Arc-Heated Supersonic Free-Jet of Nitrogen Atoms for the Growth of GaN, AlN, and InN Thin Films

摘要

Arc discharge and corona discharge supersonic free-jets are of interest as sources of 'activated' nitrogen for molecular beam epitaxy (MBE) of nitride materials. Although the current objective is growth of III-V nitride semiconductors, these discharge sources are also very relevant to MBE of silicon-oxynitride gate dielectrics. Of interest in both applications is the relative ease and simplicity with which molecular species can be dissociated and/or electronically excited in electrical discharges. Very high temperatures may be attained in an arc discharge, allowing even the strong (9.76 eV) bond of the nitrogen molecule to be broken. If less power is required, as in non- dissociative electronic excitation, the lower power of the simpler corona discharge often suffices. By striking either type of discharge at the throat of a supersonic nozzle, a highly nonequilibrium distribution of dissociated and/or excited species from can be 'frozen in' in the ensuing supersonic expansion, providing an intense beam of dissociated nitrogen atoms and/or excited nitrogen molecules. The exact spectrum of excited and/or dissociated species is determined by the type and power of the discharge. Both arc and corona discharge free-jet sources were constructed and tested in this work. The arc discharge supersonic free-jets (AD-SFJ) yielded beams consisting of up to 80% N atoms ((caret)1x10 (exp 18) atoms /sr/s) accompanied by undetermined amounts of excited atoms and molecules.