A high-quality GaSe single crystal was grown by the Bridgman method. The X-ray rocking curve for the studied GaSe sample is symmetric and the Full Width at Half Maximum (FWHM) is only 46 arcs, which is the smallest value ever reported for GaSe crystals. The IR-transmittance is about 66% in the range from 500 to 4000 cm-1. The photoluminescence spectrum at 9.2 K shows a symmetric and sharp excition peak in 2.1046 eV. The results indicate that the as-grown GaSe crystal is of high crystalline quality. The as-grown ε -GaSe crystal has a p-type conductance with the resistivity of 10³ Ω/cm, and the Hall mobility is ~25 cm² V-1 s-1. Few-layer GaSe crystals were prepared through mechanical exfoliation from this high-quality crystal sample. Few-layer GaSe-based photodetectors were fabricated, which exhibit an on/off ratio of 10⁴, a field-effect differential mobility of 0.4 cm² V-1 s-1, and have a fast response time less than 60 ms under light illumination.
Keywords: crystalline quality; photodetector; two-dimensional materials; ε-GaSe.