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

• Published in: Advanced optical materials 2024-03, Vol.12 (9), p.n/a
• Main Authors: Yang, Huarong, Cheng, Tong‐Huai, Ouyang, Huijia, Xin, Qian, Liu, Yiyuan, Meng, Miao, Yu Feng, Hua, Luo, Feng, Mu, Wenxiang, Jia, Zhitai, Tao, Xutang
• Format: Article
• Language: English
• Subjects: Controllability; Dark current; enhancement‐mode phototransistor; FIB etching; Gallium oxides; Incident light; Ion beams; low‐dimensional; Phototransistors; Plasma etching; Quantum efficiency; Reproducibility; Thickness; β‐Ga2O3 microflakes
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202302213

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. Focused ion beam (FIB) processing is introduced to etch and thin β‐Ga2O3 microflakes, which overcomes the poor controllability and low repeatability associated with the mechanical exfoliation method, as well as the residual impurities from the plasma etching method. The fabricated phototransistors switch from depletion mode to enhancement mode as the microflake thickness decreases, and the latter one exhibits an extremely low dark current without a gate voltage.