Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 28: Optische Eigenschaften

HL 28.9: Talk

Wednesday, March 10, 2004, 17:15–17:30, H17

Impact of oxidation on InN layer properties investigated by Spectroscopic Ellipsometry — •Tobias L. Schenk, Torsten Schmidtling, Massimo Drago, Christoph Cobet, and Wolfgang Richter — TU Berlin, PN6-1, Hardenbergstr. 36, 10623 Berlin

MOVPE grown InN films on sapphire by Spectroscopic Ellipsometry (SE) in the range of 0.8-6.5eV have been investigated. The observed range is extended to include the newly assumed band gap position of about 0.9eV. The exact position is indeed unknown yet, since oxidation, poor layer quality, and high number of intrinsic defects influence the optical properties. An important fact seems to be the oxidation of the still defective layers. Therefore MOVPE grown layers in different grades of oxidation are prepared and studied under controlled conditions and also compared to MBE grown and sputtered ones. We find a strong dependence of the band gap position on the oxidation state. This demonstrates that oxidation is a critical factor contributing to the uncertainty of the determination of the band gap value. Furthermore the oxidation influence on the optical constants is evident in the whole spectral region leading to a strong decrease in the dielectric response of the higher transitions.