MOCVD growth of thick AlN and AlGaN superlattice structures on Si substrates

A number of applications require deposition of thick, high-quality AlN films with low stress on Si substrates. Conventional high-temperature MOCVD growth produced an AlN film that exhibited cracking for a film thickness greater than 300 nm due to the large tensile stress generated during the growth process. Alternative methods, including the introduction of low-temperature AlN interlayers, were developed to control the strain developed during MOCVD growth of thick AlN on Si. Additionally, an alternating sequence of AlN and AlGaN—with up to 70% AlN—in a superlattice structure was found to decrease cracking in the films. Structures with thin crack-free GaN cap layers were demonstrated.