Disorder-activated infrared modes and surface depletion layer in highly Si-doped hexagonal GaN

A. Kasic, M. Schubert, B. Kuhn, F. Scholz, S. Einfeldt, D. Hommel

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

Three infrared-active low-polar modes are reported for highly Si-doped hexagonal (α-) GaN. The 0.8-1.6 μm thick films, grown by metal organic vapor phase epitaxy or molecular beam epitaxy on (0001) sapphire substrates, were studied by infrared spectroscopic ellipsometry. For GaN epilayers with free-electron concentration N≥8×1018 cm-3 we observe, besides the usual GaN transverse-optical lattice modes and coupled longitudinal-optical phonon-plasmon modes, a band of additional modes at 567.4±2.5, 752.5±0.9, and 855.0±0.9 cm-1. We tentatively assign the first one to the disorder-activated high E2 GaN mode and the third mode to an acoustic-optical combination band, whereas the origin of the second mode remains unclear. Furthermore, the ellipsometric spectra of highly n-conductive Si-doped GaN reveal thin carrier-depleted regions at the sample surface.

Original languageEnglish (US)
Pages (from-to)3720-3724
Number of pages5
JournalJournal of Applied Physics
Volume89
Issue number7
DOIs
StatePublished - Apr 1 2001

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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