In situ determination of surface composition, polarity, crystallographic relationship, and periodicity of GaN films by mass spectroscopy of recoiled Ions and direct recoiled spectroscopy

Abstract

Applicability of time-of-flight (TOF) mass spectroscopy of recoiled ions (MSRI) and direct recoiled spectroscopy (DRS) as in situ techniques for both optimization and characterization of thin film materials is presented in this article. TOF DRS/MSRI were used to monitor the growth process of GaN and (Ga,Mn)N by chemical-beam epitaxy. We show that all important growth parameters can be optimized real time and that under our experimental conditions, all epilayers are metal polar, as confirmed ex situ by wet etching. The surface periodicities of c-sapphire and the final GaN and (Ga,Mn)N epilayers were determined and found to be parallel to each other, but with a 30° in-plane relative rotation between them—as reported by several researchers. Finally, analysis of the Ga and Mn azimuthal surface signals supports that for all concentrations (0.5% to 2.5%) in our studies, the Mn atoms are substitutional into the GaN crystal structure.