Structural, optical and mechanical properties of Cr doped β-Ga2O3 single crystals

Abstract

Undoped and Cr doped β-Ga₂O₃ (100) single crystals are grown by optical floating zone method. The full width at half maximum of rocking curve is found to be 106 arc.sec for undoped β-Ga₂O₃ crystals whereas the 100 and 200 ppm of Cr doped β-Ga₂O₃ crystals display multiple rocking curves with large peak widths indicating the presence of structural defects. Raman measurements reveal broadening in the vibrational mode of ~ 350 cm^− 1 with a shoulder peak indicating the Cr³⁺ dopants preferentially substitute for Ga³⁺ at the octahedral sites. Further, the Cr doped β-Ga₂O₃ crystals display strong optical absorption bands about 420 and 597 nm in the UV-Vis spectroscopy. Moreover, the observation of sharp characteristic photoluminescence emission lines at 690 and 697 nm also confirms the Cr substitution in the doped crystals. The indentation hardness increases nearly linear from 13.0 ± 0.6 to 17.9 ± 0.4 GPa whilst the indentation modulus decreases from 224.9 ± 21.4 to 202.4 ± 11.9 GPa upon Cr doping of 200 ppm in β-Ga₂O₃. The structural defects caused by the Cr doping interrupt the movement of indentation induced dislocations that results in the increase of hardness of the Cr doped β-Ga₂O₃ (100) single crystals.