Effect of AlN interlayer on the impurity incorporation of GaN film grown on sputtered AlN

We investigated the influence of AlN interlayer with varied V/III ratio on the impurity incorporation of GaN films grown on sputtered AlN layer by metal organic chemical vapor deposition (MOCVD). It is found that the V/III ratio of AlN interlayer significantly influences on the growth mode and leads different impurity distribution and electron properties. In the case of AlN interlayer with an optimized V/III ratio, incorporation of oxygen impurity in GaN epitaxial films is suppressed. Leading to the GaN film shows a high sheet resistivity. However, at a lower V/III ratio, an unexpected three-dimensional growth mode plays dominant role. While at a higher V/III ratio, the GaN polarity would invert to N-polar. Both these two situations would deteriorate the electrical properties of GaN film.