Growth and characterization of free-standing zinc-blende GaN layers and substrates

We have investigated the growth of bulk, free-standing zinc-blende (cubic) GaN layers by plasma-assisted molecular beam epitaxy (PA-MBE). The PA-MBE technique was used for bulk crystal growth and GaN layers up to 100 µm in thickness were produced. We have established that the best structural properties of free-standing zinc-blende GaN can be achieved with initiation under Ga-rich conditions, but without Ga droplet formation. The procedure to produce free-standing bulk zinc-blende substrates from thick GaN layers grown on GaAs substrates has been developed. We have demonstrated the scalability of the process by growing free-standing GaN layers up to 3 in. in diameter. Growth of free-standing bulk GaN layers has allowed us to refine the values for the basic parameters of zinc-blende GaN. We have demonstrated also that the PA-MBE process we have developed has allowed us to achieve free-standing AlxGa1−xN wafers.