SKM 2023 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 41: Oxide Semiconductors I: Ga₂O₃

HL 41.4: Talk

Thursday, March 30, 2023, 15:45–16:00, POT 81

Anisotropic IR active phonon modes and fundamental direct band-to-band transitions in α-(Al_xGa_1−x)₂O₃ alloys grown by MOCVD — •Elias Kluth¹, A F M Anhar Uddin Bhuiyan², Lingyu Meng², Hongping Zhao², Rüdiger Goldhahn¹, and Martin Feneberg¹ — ¹Institut für Physik, Otto-von-Guericke-Universität Magdeburg, Germany — ²Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio, USA

The corundum-like Ga₂O₃ polymorph α-Ga₂O₃ is of high research interest as it allows bandgap-engineering by alloying e.g. with α-Al₂O₃, α-In₂O₃, α-Ti₂O₃ and similar materials. Since the corundum-like crystal structure is anisotropic, a direction dependent investigation of the material properties is crucial. m-plane α-(Al_xGa_1−x)₂O₃ thin film samples up to x=0.76, grown on m-plane sapphire substrate by MOCVD have been investigated by infrared (IR) and visible-ultraviolet (UV) spectroscopic ellipsometry. IR ellipsometry yields the anisotropic IR active phonons and their shift to higher wavenumbers with increasing x. Furthermore, with UV ellipsometry, we find the anisotropic dielectric functions up to 6.6eV and the shift of the fundamental direct band-to-band transitions with increasing x. We report an anisotropic bowing parameter for α-(Al_xGa_1−x)₂O₃ of b_ord=2.7eV and b_extra=2.5eV.