Improved Photoresponse Characteristics of a ZnO-Based UV Photodetector by the Formation of an Amorphous SnO2 Shell Layer

Junhyuk Yoo,Jinsub Park,Uijin Jung,Bomseumin Jung,Wenhu Shen

doi:10.3390/s21186124

Abstract

Although ZnO nanostructure-based photodetectors feature a well-established system, they still present difficulties when being used in practical situations due to their slow response time. In this study, we report on how forming an amorphous SnO2 (a-SnO2) shell layer on ZnO nanorods (NRs) enhances the photoresponse speed of a ZnO-based UV photodetector (UV PD). Our suggested UV PD, consisting of a ZnO/a-SnO2 NRs core–shell structure, shows a rise time that is 26 times faster than a UV PD with bare ZnO NRs under 365 nm UV irradiation. In addition, the light responsivity of the ZnO/SnO2 NRs PD simultaneously increases by 3.1 times, which can be attributed to the passivation effects of the coated a-SnO2 shell layer. With a wide bandgap (~4.5 eV), the a-SnO2 shell layer can successfully suppress the oxygen-mediated process on the ZnO NRs surface, improving the photoresponse properties. Therefore, with a fast photoresponse speed and a low fabrication temperature, our as-synthesized, a-SnO2-coated ZnO core–shell structure qualifies as a candidate for ZnO-based PDs.

Highlights

Ultraviolet (UV) photodetectors (PDs) have received much attention due to their diverse applications, such as in flame detection, optical communication, biological analysis, and emitter calibration [1,2,3]
Several metal oxide (MO) materials have been recommended for use in UV photodetector (UV PD), such as ZnO [4,5], TiO2 [6], and SnO2 [7,8]
MO materials, low-dimensional ZnO has been considered a key material for UV PDs due to its large surface–volume ratio and Debye length [9,10]

Summary

Introduction

Ultraviolet (UV) photodetectors (PDs) have received much attention due to their diverse applications, such as in flame detection, optical communication, biological analysis, and emitter calibration [1,2,3]. The slow light response speeds and high photoconductive gain exhibited by ZnO-based UV PDs are strongly related to the oxygen-mediated detection mechanism [19,20,21]. There is a trade-off between the high photoconductive gain and the fast light response speed To improve their rise and fall times without degrading the photoconductive gain, introducing a shell layer to the ZnO core, such as AIN [18], Al2 O3 [22], InN [23], SnO2 [24], PVA [25], CuCrO2 [26], or TiO2 [27], may be a promising solution, resulting in an improvement in the overall performance of PDs. forming the shell layer of these materials requires a high temperature and is a complex and expensive process. SnO2 can be used as a shell material for ZnO due to its excellent properties, including a wide direct band gap, high transparency with high mobility, and excellent stability [28,29]

Methods

Results

Conclusion