Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al
| Autor: | Mike Pietsch, Andreas Fiedler, Zbigniew Galazka, Matthias Bickermann, Robert Schewski, Steffen Ganschow, Martin Albrecht, Detlef Klimm, Klaus Irmscher, Rainer Bertram |
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| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Materials science Dopant Band gap Doping Analytical chemistry Crystal growth 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Inorganic Chemistry Crystal Absorption edge 0103 physical sciences Materials Chemistry 0210 nano-technology Absorption (electromagnetic radiation) Monoclinic crystal system |
| Zdroj: | Journal of Crystal Growth. 486:82-90 |
| ISSN: | 0022-0248 |
| Popis: | We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1–1.5 at 7–24 vol% O2, while for Ce they are roughly below 0.01 at 1.5–34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5–21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1−x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV. |
| Databáze: | OpenAIRE |
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