Photodarkening and dopant segregation in Cu-doped β-Ga2O3 Czochralski single crystals

•Cu-doped β-Ga2O3 was grown via Czochralski and vertical gradient freeze methods.•Crystals displayed novel photodarkening with UV excitation, stable at room temp.•Photodarkening is reversible back to as-grown state with an anneal at 400 °C.•Dopant segregation was shown via laser ablation inductively...

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Bibliographic Details
Published in:Journal of crystal growth 2022-01, Vol.578, p.126419, Article 126419
Main Authors: Jesenovec, Jani, Remple, Cassandra, Huso, Jesse, Dutton, Benjamin, Toews, Parker, McCluskey, Matthew D., McCloy, John S.
Format: Article
Language:English
Subjects:
A1. Doping
A1. Segregation
A2. Czochralski method
B1. Gallium compounds
B1. Oxides
B2. Semiconducting gallium compounds
Copper
Crystal structure
Dopants
Doping
Electrical measurement
Electrical properties
Gallium oxides
Inductively coupled plasma mass spectrometry
Laser ablation
Mass spectrometry
Optical properties
Photodarkening
Photoluminescence
Raman spectroscopy
Room temperature
Single crystals
Ultraviolet radiation
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Summary:•Cu-doped β-Ga2O3 was grown via Czochralski and vertical gradient freeze methods.•Crystals displayed novel photodarkening with UV excitation, stable at room temp.•Photodarkening is reversible back to as-grown state with an anneal at 400 °C.•Dopant segregation was shown via laser ablation inductively coupled mass spec. β-Ga2O3 has demonstrated insulating properties with Mg, Fe, and Zn acceptor doping. Here we investigate Cu doping (0.25 at.%) in bulk Czochralski (CZ) and vertical gradient freeze (VGF) β-Ga2O3, with significant Cu incorporation, even with the expected Cu evaporation. Representative crystals were assessed for orientation, purity, optical, and electrical properties. The solubility and electronic behavior of Cu dopants are consistent with measured concentrations of 1 × 1018–1 × 1019 atoms/cm3 and electrical measurements that show high resistivities of 109–1010 Ω∙cm. Segregation and precipitation of Cu species in part of the VGF material was determined to be Cu2O by analysis with Raman spectroscopy, photoluminescence microscopy, energy-dispersive X-ray spectroscopy, and laser ablation inductively coupled plasma mass spectrometry. With sufficient Cu concentration, β-Ga2O3 crystals excited with deep ultraviolet light photodarken rapidly and exhibit decreased resistivity. This darkened state remains at room temperature for several days before decaying.
ISSN:0022-0248
1873-5002
DOI:10.1016/j.jcrysgro.2021.126419