Dramatic reduction in dark current of β-Ga<sub>2</sub>O<sub>3</sub> ultraviolet photodectors via β-(Al<sub>0.25</sub>Ga<sub>0.75</sub>)<sub>2</sub>O<sub>3</sub> surface passivation
Jianying Yue, Xueqiang Ji, Shan Li, Xiaohui Qi, Peigang Li, Zhenping Wu, Weihua Tang
Abstract
Solar-blind ultraviolet photodetectors with metal-semiconductor-metal structure were fabricated based on β -(Al 0.25 Ga 0.75 )x 2 O 3 / β -Ga 2 O 3 film grown by metal-organic chemical vapor deposition. It was known that various surface states increase dark current and a large number of defects can hinder the transport of carriers, resulting in low switching ratio and low responsivity of the device. In this work, β -(Al 0.25 Ga 0.75 ) 2 O 3 films are used as surface passivation materials. Owning to its wide band gap, we obtain excellent light transmission and high lattice matching with β -Ga 2 O 3 . We explore the change and mechanism of the detection performance of the β -Ga 2 O 3 detector after β -(Al 0.25 Ga 0.75 ) 2 O 3 surface passivation. It is found that under the illumination with 254 nm light at bias 5 V, the β -(Al 0.25 Ga 0.75 ) 2 O 3 / β -Ga 2 O 3 photodetectors show dark current of just 18 pA and high current on/off ratio of 2.16 × 10 5 . The dark current is sharply reduced about 50 times after passivation of the β -Ga 2 O 3 surface, and current on/off ratio increases by approximately 2 times. It is obvious that β -Ga 2 O 3 detectors with β -(Al 0.25 Ga 0.75 ) 2 O 3 surface passivation can offer superior detector performance.