PVT growth of GaN bulk crystals

Limitations in ammonia-based vapour growth of bulk GaN require the search for a replacement of ammonia as a precursor of reactive nitrogen. We propose the implementation of a plasma-activated nitrogen source instead. In this contribution we present the current development status of a long-term stable plasma source for reactive nitrogen supply as well as a novel gallium source setup, both of which serve as the basis of a new approach to grow GaN bulk crystals. Following the characterization of the Ga source, the evaporation energy was determined as (284±9) kJ/mol and the transport becomes saturated at a carrier gas flow of 200 sccm N2. Short microwave pulses are applied to operate the plasma source. Crystal growth conditions require high power and stable currents of the microwave pulses - which will be achieved using a custom-built power supply - to reduce the thermal loads at the desired high-pressure operation.