Indium surfactant assisted molecular beam epitaxy of AlScN
Pierce Lonergan, Thai‐Son Nguyen, Chandrashekhar Savant, Henryk Turski, Huili Grace Xing, Debdeep Jena
Abstract
The epitaxial growth of AlScN on GaN has been traditionally performed in the nitrogen-rich condition because growth in metal-rich conditions results in the formation of Al–Sc intermetallic precipitates. Nitrogen-rich growth conditions promote island formation and roughen the surface, which is typically avoided in metal-rich growth conditions. In this work, we identify a wide window of practical growth conditions for AlScN/GaN heterostructures in which the use of indium during the growth of the AlScN layers helps mimic metal-rich growth conditions while preventing the incorporation of indium into the AlScN epitaxial layer. As a result of indium acting as a surfactant, AlScN surfaces with rms roughness as low as 0.36 nm and exhibiting step morphology are observed. We find that the growth of AlScN outside this surfactant-window results in indium incorporation at low growth temperatures or pit formation at high indium fluxes. These findings provide an alternative growth technique for highly crystalline AlScN/GaN heterostructures that overcomes limitations of nitrogen-rich growth conditions by using indium as a surfactant.