Arsenic incorporation and growth mode of GaNAs grown by low-pressure metal-organic chemical vapor deposition

GaNAs epilayers were grown on GaN/sapphire substrates by low-pressure metal-organic chemical vapor deposition, Tertiarybutylarsine (TBAs) was used as the As source. The As contents in the GaNAs epilayers was measured by secondary ion mass spectrometry. and the surface morphology was studied by atomic force microscopy. The As contents in GaNAs increased drastically with decreasing growth temperature, and became saturated at 5 x 10(20) cm(-3) at 565degreesC. This As incorporation behavior is attributed to the temperature dependence of NH3 decomposition and the weaker Ga-As bond. When GaNAs was grown above 565degreesC. the GaNAs surface was granular with typical granule size of several ten nm. Size and density of the granules depend on the TBAs flow rate. At 530degreesC, not only a GaN phase but also a GaAs phase was observed by X-ray diffraction with very large islands on a flat surface. It is believed that excessive As incorporation results in the formation of large islands. (C) 2002 Elsevier Science B.V. All rights reserved.