Visualization of twin formation of β-Ga2O3 by edge-defined film-fed growth

Abstract

β-Phase gallium oxide (β-Ga₂O₃) crystals prepared by an edge-defined film-fed growth (EFG) method usually suffer from high density of twins, which severely affects the quality of the epitaxial layer and the performance of devices. Twinning is a type of planar defect in the β-Ga₂O₃ crystal in a range from the millimeter-scale to nanometer-scale. During the crystal growth process, the temperature fluctuation on the top die as well as a mismatch between the pulling speed and the crystallization rate would leave the (100) facet exposed, which increases the possibility of twin formation. The crystal orientation of the β-Ga₂O₃ wafers has been observed by electron backscattered diffraction (EBSD), reflecting the distribution and size of the twins in the crystals. By optimizing the pulling speed and crystallization rate, a steady shoulder process has been realized. Twin-free (01) oriented β-Ga₂O₃ crystals have been successfully prepared by EFG growth with outstanding crystalline quality in this work. An innovative means of detection of twins has also been proposed by high resolution X-ray diffraction (HRXRD) measurement, which supplies a quick and non-destructive way for routine testing of the β-Ga₂O₃ wafers.