Regensburg 2004 – scientific programme
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HL: Halbleiterphysik
HL 27: GaN: Pr
äparation und Charakterisierung
HL 27.15: Talk
Wednesday, March 10, 2004, 18:45–19:00, H15
Electro-optic Effects in Nitride Semiconductors: Investigation and Application for Characterisation — •S. Shokhovets1, G. Gobsch1, O. Ambacher2, M. Hermann3, and M. Eickhoff3 — 1Institute of Physics, TU Ilmenau, PF 100565, 98684 Ilmenau, Germany — 2Center for Micro- and Nanotechnologies, TU Ilmenau, PF 100565, 98684 Ilmenau — 3Walter Schottky Institute, TU Munich, Am Coulombwall 3, 85748 Garching
We report on the results of electroreflectance (ER) and impedance-voltage (ZV) studies of GaN and AlGaN diodes with a semitransparent Pt Schottky gate. The data analysis was carried out using the multi-layer formalism which allows us to consider the electric field inhomogeneity. The field-dependent contribution of excitons and excitonic continuum to the dielectric function (a) and the linear electro-optic effect (b) were identified to be the main mechanisms of the electro-optical response. The first effect leads to the so-called rotation ER spectra in a region of the excitonic absorption and reduces to the Franz-Keldysh-like oscillations above the band gap. The second one is responsible for the electro-optical response below the band gap. Further, applications for characterisation (exciton energies and broadening parameters for the zero-field limit, band bending, concentration of ionised impurities and electric field strength in the depletion region as a function of the temperature) are presented and compared with the ZV measurements.