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arXiv · 2505.03685

Leveraging high fluence and low pressure for pulsed laser deposition of high-mobility $γ$-Al$_2$O$_3$/SrTiO$_3$ heterostructure growth

Thor Hvid-Olsen·Christina Hoegfeldt·Amit Chanda·Alessandro Palliotto·Dae-Sung Park·Thomas Sand Jespersen·Felix Trier
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Abstract

High-mobility oxide heterostructures could be applied for high-frequency devices, transparent conductors, and spin-orbit logic devices. SrTiO$_3$ is one of the most studied oxide substrate materials for heterostructures. To date, the highest SrTiO3-based charge carrier mobility at 2 K was measured in the interfacial 2-dimensional electron gas (2DEG) of $γ$-Al$_2$O$_3$/SrTiO$_3$. The formation mechanism and origin of the high electron mobility are not yet fully understood. This investigation presents a successful growth protocol to synthesise high mobility $γ$-Al$_2$O$_3$/SrTiO$_3$ interfaces, and a description of the underlying growth optimisation. Furthermore, indicative features of high-mobility $γ$-Al$_2$O$_3$/SrTiO$_3$, including the room-temperature sheet resistance, are presented. Signs of epitaxial and crystalline growth are found in a high-mobility sample ($μ^{10K} = 1.6 \times 10^4 \mathrm{cm}^2/\mathrm{Vs}$). Outlining the growth mechanisms and comparing 40 samples, indicates that high-fluence ($F > 3\mathrm{J}/\mathrm{cm}^2$) and low pressure ($P \approx 1 \times 10^{-6} \mathrm{mbar}$) are essential growth parameters for high-mobility $γ$-Al$_2$O$_3$/SrTiO$_3$ interfaces. $γ$-Al$_2$O$_3$ having single-element cations allows higher laser fluences during growth, compared to thin films with multi-element cations such as LaAlO$_3$, without causing stoichiometric imbalances.

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Thor Hvid-Olsen, Christina Hoegfeldt, Amit Chanda, Alessandro Palliotto, Dae-Sung Park, Thomas Sand Jespersen, Felix Trier. 2025-11-11. Leveraging high fluence and low pressure for pulsed laser deposition of high-mobility $γ$-Al$_2$O$_3$/SrTiO$_3$ heterostructure growth. https://doi.org/10.1063/5.0278792

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