Ferroelectric Depolarization-Field-Enhanced Ag/ZnO/Si:Ga<sub>2</sub>O<sub>3</sub>/BFMO/FTO Multijunction Self-Driven Photodetector with Ultrahigh Performance
Yingying Cheng, Jiaxing Mao, Yanhui Dong, Pan Wang, Teng Zhang, Jian Chen, Mingkai Li, Yinmei Lu, Yunbin He
Abstract
We demonstrate herein a novel ferroelectric depolarization-field ( E dp )-enhanced Ag/ZnO/Si:Ga 2 O 3 /BFMO/FTO multijunction photodetector, which delivers ultrahigh self-driven detection performance in terms of responsivity ( R ) and detectivity ( D *) toward ultraviolet (UV) band (200–300 nm) signals. Owing to the superposition of various interfacial electric fields (i.e., E ZnO/Si:Ga2O3, E Si:Ga2O3/BFMO, and E BFMO/FTO ), the unpoled Ag/ZnO/Si:Ga 2 O 3 /BFMO/FTO multijunction device exhibits much higher R (46.6 mA/W) and D * (1.02 × 10 12 Jones) than the Ag/Si:Ga 2 O 3 /BFMO/FTO dual-junction device ( R = 25.3 mA/W; D* = 6.20 × 10 11 Jones) and the Ag/Si:Ga 2 O 3 /FTO single-junction device ( R = 12.5 mA/W; D* = 3.33 × 10 11 Jones). Moreover, the Ag/ZnO/Si:Ga 2 O 3 /BFMO/FTO device, when upward poled, shows 9 and 9.8% further enhancement in R (50.8 mA / W) and D* (1.12 × 10 12 Jones), respectively, compared to the unpoled state. The device exhibits short rise/decay (τ r /τ d ) response times of 4.4/17.3 ms due to the multiple electric-field-derived rapid separation of photogenerated carriers. The device shows even higher photodetection performance with an R of 103.9 mA/W and a D * of 2.29 × 10 12 Jones under weak light illumination ( P 260 nm = 0.001 mW/cm 2 ). These parameters surpass those of the most previously reported Ga 2 O 3 -based self-driven photodetectors. The present work indicates that the strategy of introducing multiple built-in electric fields to synergistically separate photogenerated carriers offers an effective approach for the development of high-performance optoelectronic devices including Ga 2 O 3 -based self-driven photodetectors.