Volume Gallium Oxide Crystals Grown from Melt by the Czochralski Method in an Oxygen-Containing Atmosphere
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Gallium Oxide Crystals Grown from Melt by the Czochralski Method in an Oxygen-Containing Atmosphere D. A. Zakgeima,b, D. I. Panova*, V. A. Spiridonova, A. V. Kremlevaa, A. M. Smirnova, D. A. Baumana, A. E. Romanova,b, M. A. Odnoblyudova,c, and V. E. Bougrova a
St. Petersburg National Research University of Information Technologies, Mechanics, and Optics (ITMO University), St. Petersburg, 197101 Russia b Ioffe Physical Technical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia c Peter the Great St. Petersburg Polytechnic University, St. Petersburg, 195251 Russia *e-mail: [email protected] Received August 5, 2020; revised August 5, 2020; accepted August 16, 2020
Abstract—Results of successful experiments on the growth of gallium oxide (β-Ga2O3) crystals by the Czochralski method are reported. The influence of growth atmosphere on the crystalline perfection of obtained material has been studied. It established that high-quality transparent optical crystals can be obtained provided the atmosphere contains about 5 vol % oxygen. As-grown β-Ga2O3 crystals were characterized by X-ray diffraction and optical transmission measurements. Keywords: gallium oxide, pulling from melt, Czochralski method, oxygen vacancies. DOI: 10.1134/S1063785020110292
In recent years, there has been strongly increased interest in the new wide-bandgap semiconductor material—crystalline gallium β-oxide (β-Ga2O3) [1, 2]. A large bandgap value (4.9 eV), relatively high electron mobility (above 150 cm2/(V s)), high breakdown field (8 MV/cm), and transparency in the visible and UV spectral range make this material highly promising in numerous applications of micro-, opto-, and power electronics. In particular, β-Ga2O3 can be used for the creation of devices possessing record high characteristics such as metal–semiconductor–oxide (MOS) transistors with breakdown voltages above 1000 V [3] and can serve as transparent conducting substrate for expitaxial growth of Group III nitrides [4]. An important advantage of gallium oxide over nitride semiconductors (GaN, AlN) is relatively simple technology of obtaining its volume single crystals. It is common practice to grow β-Ga2O3 crystals by the well-known methods of Stepanov [5], Czochralski [6, 7], and zone melting [8], among others. However, the growth from melt is complicated by the chemical instability of β-Ga2O3 at the melting temperature [6]. This circumstance hinders the obtaining of high-quality material in an inert growth atmosphere and requires introducing oxygen in amounts from several units to several dozen volume percent [7]. The presence of oxygen in the growth reactor atmosphere in combination with rather high melting temperature of
gallium oxide (1850°C) poses significant restrictions on the choice of materials for crucibles and other parts of technological equipment (made in most cases of iridium). This Letter reports on our successful experience in growing high-quality β-Ga2O3 single crystals from melt by the Czochralski method. The influence of growth atmosphere (pa
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