Plasma assisted molecular beam epitaxy of GaN with growth rates >2.6 Amm/h

Plasma-assisted molecular beam epitaxial (PAMBE) growth of gallium nitride (GaN) was explored with a novel modification of a commercially available nitrogen plasma source. The modified nitrogen plasma source enabled a dramatic increase in the flux of active nitrogen and thus a significantly higher growth rate than has been previously reported. GaN films were grown using N2 gas flow rates between 1 and 8 sccm while varying the plasma source's RF forward power from 200 to 600 W. The highest growth rate, and therefore the highest active nitrogen flux achieved was ~2.65 mu m/h. For optimized growth conditions the surfaces displayed a clear step-terrace structure with an average RMS roughness (3 AmmA3 Amm) on the order of 1 nm. Secondary ion mass spectroscopy (SIMS) impurity analysis demonstrates oxygen and hydrogen incorporation of 1A1016 and 5A1016 respectively, comparable to the metal organic chemical vapor deposition (MOCVD) grown template layer. Initial un-optimized electron mobility measurements of 1 Amm thick GaN layers have shown a peak mobility of ~705 cm2/V s for an electron concentration of ~3.5A1016 cma3. A revised universal growth diagram is proposed allowing the rapid determination of the metal flux needed to grow in a specific growth regime for any and all active nitrogen fluxes available.