Ultrasensitive self-powered broadband ultraviolet photodetectors based on n-(Ga0.9Sn0.1)2O3/n-TiO2 heterojunction

Ga ₂O ₃-based self-powered ultraviolet (UV) photodetectors (PDs) have recently attracted much interest, but they need to be fabricated via complex and expensive vacuum equipments, and the photoresponse performances are not quite good. To solve these problems, we have developed high-property (Ga _0.9Sn _0.1) ₂O ₃/TiO ₂ heterojunction UV PDs by a low-cost, effective, and facile sol-gel way. Sn ⁴⁺ possesses higher valence in comparison with Ga ³⁺, and Sn-O bonding energy is weaker than Ga-O bonding energy, which are both in favor of increasing electron concentrations of n-type Ga ₂O ₃, resulting in improved photocurrent. TiO ₂ can form type-II band alignment when it contacts with (Ga _0.9Sn _0.1) ₂O ₃, which is beneficial for separating and transporting photo-generated carriers of the heterojunction PDs. Consequently, a high responsivity of 57.86 mA/W, large detectivity of 9.33×10 ¹¹ Jones, and quick response rate with a rise/decay time of 0.05/0.66 s at a light wavelength of 230 nm and 0 V bias are achieved in the Au/(Ga _0.9Sn _0.1) ₂O ₃/TiO ₂/FTO heterojunction PDs. More encouragingly, because the (Ga _0.9Sn _0.1) ₂O ₃ and TiO ₂ possess strong absorption characteristics for UVC, and UVB and UVA light, respectively, the heterojunction self-powered PDs present superior broadband detection capacity across ultraviolet A to ultraviolet C spectrum.