Enhancement‐Mode Phototransistors Based on β‐Ga₂O₃ Microflakes Fabricated by Focused Ion Beams

Abstract This study introduces focused ion beam (FIB) processing for the first time to etch and thin β‐Ga₂O₃ microflakes, while exploring the effect of their thicknesses on the phototransistor performance. It is found that when the β‐Ga₂O₃ microflakes reach a certain thickness, the phototransistors switch from the depletion mode to the enhancement mode, exhibiting extremely low dark current without a gate voltage. The enhancement‐mode phototransistor prepared using this method demonstrates a photo‐dark current ratio as high as 2.3 × 10⁵, a responsivity of 6.3 × 10⁴ A W⁻¹, and an external quantum efficiency of 3.1 × 10⁷% when irradiated with incident light at a wavelength of 254 nm and a power density of 8 µW cm⁻². Additionally, the device has a rise time of 43 ms and a fall time of 28 ms, respectively. By using FIB processing to etch and thin β‐Ga₂O₃ microflakes, this study effectively overcomes the poor controllability and low repeatability associated with the traditional mechanical exfoliation method, as well as the residual impurities from the plasma etching method. This opens up a new avenue for fabricating the high‐performance, low‐dimensional phototransistors based on β‐Ga₂O₃ with high repeatability and controllability.