Forming a thick layer of ε-Ga₂O₃ on the GaN sublayer with V-defects at the interface

This report presents the results of an experiment to obtain and characterization of quasi-bulk monocrystal epitaxial ε-Ga₂O₃/GaN heterostructures which contain V-defects at the interface. The significance of this work is due to an active search for ways to develop device-heterostructures for deep-ultraviolet optoelectronics and for HEMT transistors in high-frequency and high-power electronics. One such solution is epitaxial growth of a thick ε-Ga₂O₃ layer on templates with GaN epitaxial layer to form ε-Ga₂O₃/GaN heterostructure. The ε-Ga2O3 is characterized by a wide band gap and high spontaneous polarization. The Ga₂O₃ layer was grown by chloride-hydride vapor-phase epitaxy on pre-prepared GaN/AlN/3C-SiC/Si structures. As the reactor was cooled to room temperature, the Ga₂O₃/GaN heterostructure (with an AlN buffer layer) spontaneously detached from the SiC/Si substrate due to the balance of the layer thermal expansion coefficients. The surface morphology of the gallium oxide layer and the cross-section of the interface in the Ga₂O₃/GaN heterostructures were studied using scanning electron microscopy with TESCAN MIRA 3. The phase composition and crystal quality of the Ga₂O₃/GaN heterostructures were studied by X-ray diffraction on the DRON-8 diffractometer of JSC Bourevestnik. Transmission spectra of the heterostructures were obtained by spectrophotometry using an integrating sphere. This paper demonstrates the epitaxial growth of Ga₂O₃/GaN heterostructures through chloride-hydride vapor phase epitaxy and the possibility of detaching epitaxial layers from the template. Scanning electron microscopy studies of cross-section have shown that the Ga₂O₃/GaN heterostructures contain a quasi-bulk gallium oxide with a thickness of about 100 microns. Additionally, it was also shown that the heterostructures contained V-defects on the GaN growth surface, with the Ga₂O₃ layer grow over V-defects. X-ray diffraction study revealed that the formed heterostructure contains ε-Ga₂O₃ monocrystal layer, and the fell width at half maximum intensity of the diffraction reflection curve 0,0,10 is 1.8 degrees, which indicates satisfactory quality for thick epitaxial layer. The results of the study openup the possibility to develop templates and substrates for epitaxial growth of wide-bandgap semiconductor materials. Optimization of the growth modes and geometry of such heterostructures with a thick ε-Ga₂O₃ layer is a promising area for further research.

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