N-enrichment at the GaAs1-xNx/GaAs(001) interface:: microstructure and optical properties

We have investigated the growth, the microstructure and the optical properties of the GaAs0.97N0.03/GaAs interface. Epilayers were grown at 520-550degreesC using trimethylgallium, dimethylhydrazine and arsine on GaAs(0 0 1) vicinal surfaces. A 5-6 nm thick layer of GaAsN with N-enrichment is clearly seen by cross-sectional transmission electron microscopy at the interfacial region. The nitrogen composition at the interface is twice that of the bulk epilayer (close to 1.6%) as shown by photoluminescence spectroscopy (PL) and high resolution X-ray diffraction. The PL data of several samples shows two peaks located at 1-1.1 and 1.2-1.3eV associated with the interfacial region and the bulk layer, respectively. We discuss several mechanisms for the nitrogen enrichment by comparing the GaAsN film thickness. The step/terrace surface morphology of GaAs before growth is probably the key parameter. (C) 2002 Elsevier Science B.V. All rights reserved.