The effect of the first GaN monolayer on the nitridation damage of molecular beam epitaxy grown GaN on GaAs(001)

The initial molecular beam epitaxy growth of GaN on GaAs(001) was studied b y real-time monitoring of the (3x3) surface reconstruction and its transiti on to an unreconstructed (1x1). Various growth conditions were established by variation of the V/III ratio, i.e., the Ga flux. We characterized the ef fect of the first two strained GaN monolayers: a N-terminated GaN (3x3) mon olayer and a second unreconstructed (1x1) monolayer. A series of samples we re grown under N-rich, Ga-rich, and near-stoichiometric growth conditions. The resulting morphology of the interface region was analyzed by high-resol ution scanning electron microscopy, Auger-electron spectroscopy, and double crystal x-ray diffractometry. The N-rich and Ga-rich conditions resulted i n extensive defect formation due to the nitridation damage of the GaAs subs trate. The extent of this was found to be determined by the properties of t he first GaN monolayer. The surface roughness under optimum growth conditio ns could be as low as similar to 20 nm, defined by nanocrystalline grains, showing no observable nitridation damage. (C) 2001 American Institute of Ph ysics.