Berlin 2018 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 10: Oxide Semiconductors for Novel Devices (Focussed Session): Session II

DS 10.10: Vortrag

Montag, 12. März 2018, 17:30–17:45, E 020

Electronic Raman scattering in β-Ga₂O₃ — •Andreas Fiedler¹, Manfred Ramsteiner², Zbigniew Galazka¹, and Klaus Irmscher¹ — ¹Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany — ²Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5−7, 10117 Berlin, Germany

Currently, β-Ga₂O₃ is in the research focus as a material for power electronic devices because of its anticipated high electric break down field (≈ 8 MV/cm). For such applications, doping control is of outermost importance. Here we report on Raman spectroscopy investigations of highly n-type doped β-Ga₂O₃ single crystals. For degenerate material (n > 3 × 10¹⁸ cm⁻³), we observe Raman lines at about 282 cm⁻¹ (with a shoulder at 255 cm⁻¹) and at about 564 cm⁻¹, which cannot be assigned to first-order scattering by phonons. These lines exhibit only a weak temperature dependence and are essentially independent of the shallow donor species (Sn or Si). We attribute the doping induced Raman features to electronic Raman scattering caused by excitation of electrons from an effective-mass like donor impurity band into the conduction band. This assignment is based on the fact that the peak position of the low-frequency line coincides with the ionization energy of effective-mass like donors (≈ 36 meV) and the occurrence of the Raman signals only for doping concentrations exceeding the Mott criterion. Consequently, the high-frequency Raman line at 564 cm⁻¹ (=2× 282 cm⁻¹) is explained by second-order electronic Raman scattering.