Group III-nitrides (GaN, AlN, InN) are compound semiconductors with bandgap energies that span the range from the UV to the near IR. These materials are used to fabricate UV/green/blue laser diodes, high brightness light emitting diodes, microwave power transistors and power switching devices for applications in optical recording, solid state lighting, communications, radar and electric vehicles.
Our research is focused on the synthesis and characterization of group III-nitride thin films grown by metalorganic chemical vapor deposition (MOCVD). GaN thin films are typically grown on substrates such as sapphire and silicon carbide which have very different lattice constants and thermal expansion coefficients. These differences result in a high density of defects in the film and can also introduce stress into the films which can result in undesirable film cracking.
We are utilizing real-time optical monitoring techniques to study dynamic changes in film stress during deposition. The measured stress evolution is correlated to changes in film microstructure to provide an understanding of the mechanisms of stress generation and relaxation.
We are also investigating alternative substrates for group III-nitride heteroepitaxy including graphene and other 2D materials.