Detection of Cr impurities in GaN by room temperature cathodoluminescence spectroscopy

Trace levels of Cr impurities in epitaxial GaN grown on sapphire substrates were investigated using cathodoluminescence (CL) spectroscopy. CL emissions characteristic of Cr in an octahedral crystal field were observed from β−Ga2O3 overlayers produced on GaN by post-growth thermal annealing in dry O2. Cr luminescence was also observed from the sapphire substrates, a likely source of the Cr contaminant. The presented results illustrate the use of β−Ga2O3 overlayers as high sensitivity indicators of the presence of Cr in GaN.