CHARACTERIZATION OF ARSENIDE PHOSPHIDE HETEROSTRUCTURE INTERFACES BY SCANNING-TUNNELING-MICROSCOPY/

We have used cross-sectional scanning tunneling microscopy (STM) to st udy interface structure in arsenide/phosphide heterostructures grown b y gas-source molecular beam epitaxy. High-resolution images of a sampl e grown at 550 degrees C and consisting of GaAs interrupted at 200 Ang strom intervals with a 40 s P-2 flux reveal phosphide interlayers as w ide as 30 Angstrom and exhibiting lateral variations in structure over nanometer length scales. A similar sample grown at 450 degrees C exhi bits narrower interlayers and a lower level of phosphorus incorporatio n. Data obtained by STM have been corroborated by data from high-resol ution X-ray diffraction (HRXRD) and reflection high-energy electron di ffraction (RHEED) studies. Together, these studies provide direct info rmation about nanometer-scale grading and lateral nonuniformity of int erfaces that can occur under these growth conditions.