Correlation of the structural and optical properties of GaN grown on vicinal (001) GaAs substrates with the plasma-assisted MBE growth conditions

Molecular beam epitaxy, using a radio frequency nitrogen plasma source, was investigated for the direct growth of GaN thin films on vicinal (0 0 1) GaAs substrates. It has been found possible to grow GaN thin films with various types of crystal structure. Cubic (0 0 1) GaN with epitaxial relationship to the GaAs substrate could be grown without GaAs nitridation and under stoichiometric N/Ga flux ratio conditions. Hexagonal mixing in the cubic GaN films occurred mainly as domains with the [0 0 0 1] oriented parallel to the GaAs surface normal. Their origin was related to irregularities at the GaAs surface, produced by interaction with the N-beam. Layers which exhibited intense 17 K photoluminescence with the main peak; at approximately 3.42 eV, presented a polycrystalline hexagonal structure with a domain width of several 100 nm. These layers did not exhibit a "yellow-band" luminescence. (C) 2001 Elsevier Science B.V. All rights reserved.