Abstract
Ultraviolet (UV) photodetectors (PDs) have attracted significant attention for civil and military applications. Zinc-oxide (ZnO) and nickel-oxide (NiO) have been widely applied in UV-PDs owing to their wide bandgap (3.2–3.8 eV), transparency, excellent optical and electrical properties, and good chemical stability. However, UV signals are generally weak; hence, UV-PDs with high optical gain are essential. In this work, high-performance solar-blind p-NiO/n-ZnO/p-Si heterojunction bipolar phototransistors (HBPTs) were fabricated. The fabricated HBPTs exhibited a high responsivity of 9.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> A/W at a wavelength of 280 nm with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V<sub>CE</sub></i> = –7 V, a high optical gain of 3.96 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> , and a large detectivity of 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> Jones. In addition, the UV/visible rejection ratio was as high as 880. These behaviors indicate that the prepared HBPTs are good solar-blind photodetectors and suitable for the detection of weak UV signals. However, for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V<sub>CE</sub></i> value below –7 V, (| <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V<sub>CE</sub></i> | > 7V), the optical gain decreased owing to the punch-through effect. Furthermore, band-diagrams showed that the photogenerated electrons were blocked by the potential barrier at the NiO/ZnO interface (base–emitter junction) owing to a large conduction-band discontinuity (Δ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E<sub>C</sub></i> ) of 2.7 eV, which resulted in a large optical gain in the prepared HBPTs.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
