Assessment of layer composition and thickness in AlGaN/GaN HEMT structures by spectroscopic ellipsometry

✍ Scribed by Baeumler, M. ;Müller, S. ;Köhler, K. ;Wagner, J.

• Book ID: 105363072
• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 158 KB
• Volume: 202
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200460470

✦ Synopsis

Abstract

AlGaN/GaN heterostructures for power applications, grown on sapphire substrates by metal organic vapor phase epitaxy (MOVPE) in a multiwafer reactor were analyzed by spectroscopic ellipsometry (SE). The thickness of the individual layers as well as the AlGaN bandgap energy were extracted from pseudodielectric function spectra 〈ε〉 for photon energies ranging from 2 to 5 eV. The experimental 〈ε〉 spectra were analyzed using a multilayer approach, describing the dielectric functions of the individual layers by a parametric oscillator model. The potential of the technique will be demonstrated using on‐wafer homogeneity as well as wafer‐to‐wafer variation within the same growth run in the MOVPE reactor as examples. SE was found to be capable of detecting relative variations in the Al content of 1% and the AlGaN layer thickness of 10%. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)