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HL: Fachverband Halbleiterphysik

HL 29: III-V Semiconductors I (mainly Nitrides)

HL 29.1: Vortrag

Dienstag, 27. März 2012, 09:30–09:45, EW 201

Coupled LO-Phonon-Plasmon Modes in Si- and Ge-doped GaN — •Max Bügler¹, Stephanie Fritze², Armin Dadgar², Alois Krost², and Axel Hoffmann¹ — ¹Technische Universität Berlin, Institut für Festkörperphysik, Berlin, Germany — ²Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle Physik, Magdeburg, Germany

Results of Raman spectroscopy on highly silicon and germanium doped GaN epilayers showing longitudinal-optical phonon-plasmon coupled modes are presented. Micro-Raman spectroscopy allows for spatially resolved probing of carrier concentration without the need to process electrical contacts. While it is inherently challenging to achieve high carrier concentrations (>5·10¹⁹cm⁻³) in GaN by doping with Si, doping with Ge allows for carrier concentrations up to at least 2·10²⁰cm⁻³ without deterioration of the layers surface and crystalline quality. Raman spectroscopy is utilized to determine spatial fluctuations in the incorporation of Si and to proof homogeneity of doping by Ge. Results on films with carrier concentrations ranging from 3·10¹⁸cm⁻³ to 6·10¹⁹cm⁻³ for Si-doping and up to 2·10²⁰cm⁻³ for Ge-doping are presented. The observed dependence of the LPP⁻-mode position on the carrier concentration is discussed and compared to theoretical predictions. To support the interpretation of the Raman results photoluminescence and photoluminescence excitation spectroscopy experiments are presented and discussed.