Origin of unintentional gallium incorporation into AlN spacer layer grown by metalorganic vapor phase epitaxy

This article presents the origin of unintentional gallium (Ga) incorporation into AlN spacer layers grown by metalorganic vapor phase epitaxy (MOVPE). We systematically investigated the impacts on the growth layer caused by the reactor inner walls condition, under‐layer compositions and growth temperature. The Ga incorporation is not influenced by the GaN deposits on the inner walls of the reactor, but is strongly affected by the underlying GaN layer. We found that the AlN spacer layer incorporates Ga atoms that originate from the underlying GaN layer, and the amount of Ga incorporation decreases with decreasing growth temperature. We conclude that the dominant source of unintentional Ga incorporation into an AlN spacer layer is the underlying GaN layer. Furthermore, we successfully achieved a Ga composition below 0.05, almost without unintentional Ga incorporation, by growing the AlN layers at a low temperature of 805 °C.