Regensburg 2022 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 18: Oxide Semiconductors (joint session HL/KFM)

HL 18.3: Talk

Wednesday, September 7, 2022, 10:00–10:15, H33

Growth window of α-Ga₂O₃ on m-plane sapphire by pulsed laser deposition — •C. Petersen, S. Vogt, M. Kneiß, H. von Wenckstern, and M. Grundmann — Universität Leipzig, Felix Bloch Institute for Solid State Physics, Semiconductor Physics Group, Leipzig, Germany

Due to its high bandgap of 4.6-5.3 eV and high predicted breakdown field of 8 MV/cm [1], much attention is drawn to the wide bandgap semiconductor Ga₂O₃ for applications in high-power devices. However, besides the well-studied thermodynamically stable monoclinic β-phase of Ga₂O₃, the metastable α-polymorph with corundum structure is gaining scientists’ interest. Since it is isostructural to Al₂O₃, miscibility over the entire composition range of α-(Al_xGa_1−x)₂O₃ can be achieved [2] and the growth on cost-effective sapphire substrates becomes feasible. Thereby m-plane sapphire facilitates the growth of the corundum phase [3] and allows for thin films with electron mobilities as high as 65 cm²(Vs)⁻¹ [4]. We present phase-pure α-Ga₂O₃ thin films grown on m-plane sapphire over a wide temperature range of 565 ^∘C up to 750 ^∘C with high cristallinity and surface roughnesses as low as 0.7 nm (RMS). We further demonstrate that for oxygen partial pressures above 0.001 mbar the formation of the monoclinical β-phase and spinel-defective γ-phase occurs and provide a corresponding phase diagram. Resulting samples were investigated employing X-ray diffraction, reciprocal space maps and atomic force microscopy. [1] Higashiwaki, Sc. Sci. Tech., 034001, 2016. [2] Hassa, pss-b, 2000394, 2020. [3] Kneiß, jmr, 4816-4831, 2021. [4] Akaiwa, pss-a, 1900632, 2020.