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DS: Fachverband Dünne Schichten

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

DS 10.9: Vortrag

Montag, 12. März 2018, 17:15–17:30, E 020

Thermal Conductivity of β-Ga₂O₃ Bulk and thin Films — •Martin Handwerg¹, Robin Ahrling¹, Rüdiger Mitdank¹, Günter Wagner², Zbigniew Galazka², and Saskia F. Fischer¹ — ¹Novel Materials Group, Humboldt-Universität zu Berlin, 12489 Berlin, Germany — ²Leibniz Institute for Crystal Growth, 12489 Berlin, Germany

The transparent conductive oxide β-Ga₂O₃ is of huge interest for high power electronics and optoelectronics because of its high band gap (E_G≈ 4.7 eV). Knowledge of the thermal conductivity is crucial to design stable applications.
Here, we investigate the thermal conductivity of thin MOVPE grown polycristalline β-Ga₂O₃ films on sapphire-substrates and single-crystalline, electrically conductive β-Ga₂O₃ films on insulating Mg-doped Czochralski-grown β-Ga₂O₃ substrates.
In order to measure the thermal conductivity of films and substrates, we used multiple aspects of the 3ω-method: the differential 3ω-method with a separate measurement of the substrate; a variation of multiple heater lines with different line widths and a 2ω approach.
We observe a reduction of the bulk thermal conductivity in dependence of the crystallinity and film thickness. This reduction can be explained with the reduced mean free path of the phonons due to the film thickness and grain sizes. This result, as well as an observed electrical conductivity reduction with decreasing film thickness, leads to a limitation of thermally influenced applications with films thinner than ≈150 nm or the need of an improved thermal management.