Data from: Initial nucleation of metastable γ -Ga2O3 during sub-millisecond thermal anneals of amorphous Ga2O3
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Gann, Katie; Chang, Celesta; Chang, Ming-Chiang; Sutherland, Duncan; Connolly, Aine; Muller, David; van Dover, Robert; Thompson, Michael
These files contain the data supporting all of the results in Katie Gann, et. al, Initial nucleation of metastable γ -Ga2O3 during sub-millisecond thermal anneals of amorphous Ga2O3. In this work, we found: Beta-phase gallium oxide (β-Ga2O¬3) is a promising semiconductor for high frequency, high temperature, and high voltage applications. In addition to the β-phase, numerous other polymorphs also exist and understanding the competition between phases is critical to control practical devices. The phase formation sequence of Ga2O3, starting from amorphous thin films, was determined using lateral-gradient laser spike annealing at peak temperatures of 500-1400 °C on 400 μs to 10 ms timescales, with transformations characterized by optical microscopy, X-ray diffraction, and transmission electron microscopy (TEM). The resulting phase processing map showed the γ-phase, a defect-spinel structure, first nucleating under all annealing times for temperatures from 650-800 °C. Cross-sectional TEM at the onset of γ-phase formation showed nucleation near the film center with no evidence of heterogeneous nucleation at the interfaces. For temperatures above 850 °C, the thermodynamically stable β-phase was observed. For anneals of 1-4 ms, and for all anneals below 1200 °C, small randomly oriented grains were observed. Large grains were observed for anneals below 1 ms and above 1200 °C, with textured films resulting from anneals above 4 ms and 1200 °C. The formation of the γ-phase prior to β-phase, coupled with the observed grain structure, suggests that the γ-phase is kinetically preferred during thermal annealing of amorphous films, with β-phase formation subsequently forming by nucleation at higher temperatures. The low surface energy of the γ-phase implied by these results suggests an explanation for the widely observed γ-phase inclusions in β-phase Ga2O3 films grown by a variety of synthesis methods.
Please cite as: Katie Gann, Celesta Chang, Ming-Chiang Chang, Duncan Sutherland, Aine Connolly, David Muller, Robert van Dover, and Michael Thompson. (2022) Data from: Initial nucleation of metastable γ-Ga2O3 during sub-millisecond thermal anneals of amorphous Ga2O3. [Dataset] Cornell University eCommons Repository. https://doi.org/10.7298/e0s4-0w24
This research was supported by the Air Force Research Laboratory-Cornell Center for Epitaxial Solutions (ACCESS) under Grant No. FA9550-18-1-0529, and by the SARA MURI funded by the Air Force Office of Scientific Research under award number FA9550-18-1-0136. We also acknowledge use of the Cornell Center for Materials Research Shared Facilities supported through the NSF MRSEC program (DMR-1719875), the Materials Solutions Network at CHESS (MSN-C) supported by the Air Force Research Laboratory under award FA8650-19-2-5220, and the Cornell NanoScale Facility, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (Grant NNCI-2025233).
Gallium oxide; metastable phases; laser spike annealing
Gann, K. R., Chang, C. S., Chang, M.-C., Sutherland, D. R., Connolly, A. B., Muller, D. A., van Dover, R. B., & Thompson, M. O. (2022). Initial nucleation of metastable γ-Ga 2 O 3 during sub-millisecond thermal anneals of amorphous Ga 2 O 3. Applied Physics Letters, 121(6), 062102. https://doi.org/10.1063/5.0087093
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