β-Ga₂O₃ single crystal is the semiconductor material. It has IR and UV transparent. The material can have different applications in optic and optoelectronic fields, such as photodetectors, light-emitting diodes, conductive windows, transparent field effect transistors, phosphors, high temperature oxygen sensors and substrates for field-effect transistors [1].

β-Ga₂O₃  single crystals were grown by floating zone method at URN-2-ZM machine produced in MPEI [2].

Single crystals were grown from ceramic bar obtained by ceramic technology. The seed orientation was along (010) plane. At 10 mm/h growth rate the processes were stable. The growth processes were carried out in a variety of atmospheres, such as  in air, Ar and O₂ atmosphere, under pressure of Ar and O₂ (up to 60 bar). The lengths of grown crystals were about 80 mm and diameter up to 15 mm. We used Laue method for single crystal orientation and twin definition. It was defined lattice parameters, they confirm with well-known data. We obtained transparent anisotropic single crystals with two clear marked parallel facets.

We couldn’t grow single crystal in 80% Ar + 20 % H₂ mix atmosphere (1.5 bar), because of restoration Ga₂O₃ and strong evaporation.

The color of single crystals depends of growth atmosphere (type of gas and pressure). Influences of these two factors are different. It is seems that oxidizing atmosphere promote discoloration. We obtained colorless crystals when growth was under pressure of O₂ at 60 bar, and bluish crystals when growth was in air and Ar atmosphere.

The quality of growth single crystals depends on atmosphere and pressure too. The high quality crystal was grown under high pressure of oxygen.

Color and low quality can be associated with oxygen vacancies formation during crystal growth at weak oxidizing atmosphere. So at high temperature, under low pressure and small oxygen concentration it is intensification of Ga₂O₃ decomposition [3].

Investigating transmission spectra It was occurred that colorless sample has enhanced transmission from 300 nm and over 1000 nm. Bluish samples have several bands at about 410, 480, 600 nm and sharp lose transparent in IR region. So it can be proposed that these bands correspond to oxygen vacancy appearance.

It was measured conductivities and permittivity. The results received was confirmed with assumption that oxygen vacancy appearance in violet single crystals grown at weak oxidizing condition.

β-Ga₂O₃ single crystal doped Ni was grown too. It shows a good width luminescence with maximum at 1430 nm and decay time 600 μs.

1. E. G. Villora, K. Shimamura, Y. Yoshikawa, K. Aoki, and N. Ichinose, J. Cryst. Growth 270, 420 (2004) 462-468
2. A.M. Balbashov, S.K. Egorov J. Cryst. Growth, 52 (1981) 498-504
3.  Z. Galazka, R. Ueker, K. Irmscher, M. Albrecht, D. Klimm, M.Pietsch, M. Brützam, R. Bertram, S. Ganschow, and R. Fornari, Cryst, Res. Technol. 45, No. 12, (2010) 1229-1236

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