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

Ga2O3-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 (Ga0.9Sn0.1)2O3/TiO2 heterojunction UV PDs by a low-cost, effective, and facile sol-gel way. Sn4+ possesses higher valence in comparison with Ga3+, and Sn-O bonding energy is weaker than Ga-O bonding energy, which are both in favor of increasing electron concentrations of n-type Ga2O3, resulting in improved photocurrent. TiO2 can form type-II band alignment when it contacts with (Ga0.9Sn0.1)2O3, 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 9.33x1011 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/(Ga0.9Sn0.1)2O3/TiO2/FTO heterojunction PDs. More encouragingly, because the (Ga0.9Sn0.1)2O3 and TiO2 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.