One-step exfoliation of ultra-smooth β-Ga2O3 wafers from bulk crystal for photodetectors

Abstract

High-quality bulk β-Ga₂O₃ single crystals have been grown by optimized edge-defined film-fed growth (EFG) method. The problems of cracking and polycrystals have been effectively solved by using a high-quality 1 inch-wide seed. The crystalline quality of the as-grown crystal has been confirmed by X-ray rocking curve with a full-width at half-maximum (FWHM) of 42.1 arcsec. Moreover, an economical and efficient one-step mechanical exfoliation method has been proposed to get epi-ready β-Ga₂O₃ wafers directly. The root mean square (RMS) roughness of the wafers is noted to be around 0.1 nm, which means they are comparable or even better than wafers processed by chemical mechanical polishing (CMP). The mechanism of the exfoliation method is analyzed from a crystallographic view. A photodetector is fabricated on the exfoliated wafer directly and the device is proved to show good performance in solar-blind band.