High Quality Homoepitaxial GaN Grown by Molecular Beam Epitaxy with NH 3 on Surface Cracking

Epitaxial GaN films have been grown on GaN single-crystal substrates, using on surface cracked ammonia as nitrogen precursor for molecular beam epitaxy. With this approach excellent optical and structural properties are achieved. Low-temperature photoluminescence shows well-resolved excitonic lines with record low linewidths as narrow as 0.5 meV. The transitions are attributed to excitons bound to neutral donors ((D°, X)1 at 3.4709 eV and (D°, X)2 at 3.4718 eV) and to a neutral acceptor ((A°, X) at 3.4663 eV). In addition, free exciton lines are observed at 3.4785 eV, 3.4832 eV, and 3.499 eV for excitons A, B, and C, respectively.