Abstract
Hitherto, most research has primarily focused on improving the UV sensor efficiency via surface treatments and by stimulating the ZnO nanorod (ZNR) surface Schottky barriers. However, to the best of our knowledge, no study has yet probed the intrinsic crystal defect generation and its effects on UV sensor efficiency. In this study, we undertake this task by fabricating an intrinsic defect-prone hydrothermally grown ZNRs (S1), Ga-doped ZNRs (S2), and defect-free microwave-assisted grown ZNRs (S3). The defect states were recognized by studying X-ray diffraction and photoluminescence characteristics. The large number of crystal defects in S1 and S2 had two pronged disadvantages. (1) Most of the UV light was absorbed by the defect traps and the e–h pair generation was compromised. (2) Mobility was directly affected by the carrier–carrier scattering and phonon scattering processes. Hence, the overall UV sensor efficiency was compromised based on the defect-induced mobility-response model. Considering the facts, defect-free S3 exhibited the best UV sensor performance with the highest on/off ratio, the least impulse response time, the highest recombination time, and highest gain-induced responsivity to 368 nm UV light, which was desired of an efficient passive metal oxide-based UV sensor. Our results were compared with the recently published results.
Highlights
Owing to certain limitations in optoelectronics, such as an inevitable requirement of direct and wide bandgap materials, ZnO has been researched as an alternative to Si technology
The point to ponder is that the ZnO nanorod (ZNR) dimensions were intentionally synchronized to effectively study the real essence of change in UV sensor characteristics because of crystal defect states-induced changes in mobility than in the surface-to-volume ratio
We studied the intrinsic control in defect density to improve the vertical ZNR-based passive MSM UV sensor efficiency
Summary
Owing to certain limitations in optoelectronics, such as an inevitable requirement of direct and wide bandgap materials, ZnO has been researched as an alternative to Si technology. ZnO is known for changes in optoelectronic characteristics depending on the crystal defect density. The topic is so pervasive that it leads the researchers to intensively probe into the defect density-oriented changes in optoelectronic characteristics of ZnO [10]. ZnO defect density directly depends on the growth method. Sol–gel methods, including hydrothermal method, are facile, cheap, and user-friendly methods that are in commercial use. They generally yield a low crystalline quality nanostructure. The other aforementioned methods yield high quality nanostructures, they require sophisticated equipment and involve high costs and temperatures which restrict the use of multiple substrates. We employed the MAG method for ZnO nanorod (ZNR) growth because it is facile, user friendly, commercially benign, and yields the best quality nanostructures in a few minutes
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