On-line growth control of MOCVD deposited GaN and related ternary compounds via spectroscopic ellipsometry and X-ray diffraction

Abstract

The most frequently used method for commercial growth of III-nitrides is Metal Organic Chemical Vapor Deposition (MOCVD). So far this growth method suffered from the lack of in-situ diagnostics. The MOCVD growth process excludes all techniques based on ultra high vacuum conditions. The only way to observe and analyse in-situ the growing surface at such ambient conditions is an optical probe like spectroscopic ellipsometry (SE) or X-ray diffraction. We attached a spectroscopic ellipsometer to an MOCVD-reactor equipped with optical windows for SE and reflectometry measurements. Using an algorithm, based on the virtual substrate approximation model, we could determine the layer composition in real time. We also installed on the MOCVD reactor a laboratory-size X-ray diffractometer, which allows to measure diffraction peaks of cubic GaN and related alloys without alignment of the sample. To our knowledge these are the first in-situ X-ray diffraction measurements without using a synchrotron.