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HL: Halbleiterphysik

HL 43: GaN: Pr
äparation und Charakterisierung II

HL 43.4: Vortrag

Montag, 7. März 2005, 15:45–16:00, TU P164

Selection rules for optical transitions of wurtzite InN — •P. Schley¹, R. Goldhahn¹, G. Gobsch¹, V. Cimalla¹, O. Ambacher¹, C. Cobet², N. Esser², J. Furthmüller³, F. Bechstedt³, H. Lu⁴, and W.J. Schaff⁴ — ¹Institut f. Physik, TU Ilmenau — ²ISAS Berlin — ³FSU Jena — ⁴Cornell University Ithaca

Although it is now commonly accepted that the band gap of InN is lower than the long time used value of 1.9 eV, the large deviation between recently reported data (from 0.64 to 1.4 eV) requires clarification. One of the intrinsic properties of all nitrides is that the optical response at the band gap is strongly polarisation dependent due to the splitting of the valence bands at the Γ-point of the Brillouin zone, i.e. the absorption edge of the extraordinary dielectric function (DF) is shifted with respect to the ordinary one. We observed such a behaviour in the energy range below 1 eV. The DFs were determined by spectroscopic ellipsometry investigating a-plane InN films grown by MBE on r-plane sapphire substrates. From the energetic splitting the crystal field energy is determined with ∼30 meV taking into account the calculated spin-orbit energy of 12 meV (M. Cardona, Sol. Stat. Commun 116 (2000) 421). Knowing these energies we discuss the orientation dependence of oscillator strengths for the corresponding transitions. All results provide further evidence that InN has a band gap of about 0.65 eV at room temperature.