Nonuniformities in GaN/AlN quantum wells

Abstract

Composition sensitive annular dark field imaging and electron energy-loss spectroscopy were used to determine long-range uniformities of GaN quantum wells and the sharpness of their interfaces grown in AlN matrix by molecular beam epitaxy. Low magnification annular dark field images reveal waviness along the growth plane with a period of ∼50 nm and a height ∼20 nm in one sample and significant changes of the long-range uniformity in the other. Measurements of the changes in energy-loss spectra of the Al L2,3, Ga L2,3, and N K edge across quantum well indicate that the interfaces between the quantum wells and the barriers are in most cases almost atomically sharp.