Closed‐loop MBE growth of droplet‐free GaN with very metal rich conditions using Metal Modulated Epitaxy with Mg and In

Abstract

AbstractImprovements to the Metal Modulated Epitaxy (MME) technique are achieved through computer controlled shutter transitions based on feedback from RHEED transients (S. D. Burnham and W. A. Doolittle, J. Vac. Sci. Technol. B 24, 2100 (2006) [1]), thus creating a closed‐loop control system for nitride MBE, the first of its kind. A high‐sensitivity 22 bit camera is used to determine when RHEED transients have subsided, upon which a shutter transition is initiated allowing the efficient buildup and depletion of the metal bilayer, which improves surface morphology and growth rate compared to the standard MME technique. RMS surface roughness was reduced by 41% by using this “Smart Shuttering” improvement to MME. A substantially higher peak concentration of Mg, approaching 2% atomic concentration, was achieved using the MME technique. As expected, a negligible amount of In was incorporated into the very Ga‐rich films. Using the new closed loop control system developed for MBE, the surface morphology was improved for GaN films while highly repeatable holes concentrations as high as 4.7×1018 cm–3 with 1.07 cm2/V‐sec mobility was obtained. This approach offers great promise for improved reproducibility and improved material quality. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)