Growth and optical properties of A1N homoepitaxial layers grown by ammonia-source molecular beam epitaxy

摘要

We have performed the homoepitaxial growth of high-crystalline quality Aluminium nitride (A1N) epilayers by the ammonia-gas source (GS) molecular-beam epitaxy method using the hydride vapor-phase epitaxy (HVPE) grown A1N thin layers as substrates. Surface morphologies and step-bunching structures of the homoepitaxially grown A1N epilayers were evaluated using in situ reflection high-energy electron diffraction (RHEED) patterns and scanning probe microscopy. It is noted that the step height of several monolayers was achieved on the surface of homoepitaxial layers. The homoepitaxial A1N thin films had the same or improved crystalline quality compared with the HVPE-grown A1N layers from X-ray rocking curve measurements, and its optical properties were investigated using cathodoluminescence measurements. Excitonic emission, which originates from the A free-exciton transition, was clearly observed in the present high-quality homoepitaxial A1N epilayers.