A high-sensitivity, fast-response, rapid-recovery UV photodetector based on p-GaN/NiO nanostructures/n-GaN sandwich structure
Graphical abstract
Introduction
Ultraviolet (UV) photodetectors have recently drawn attention due to their potential applications [[1], [2], [3], [4]]. For example, devices based on GaN-based semiconductor materials have potential applications in UV detection [5,6]. However, the main problem of GaN-based materials is a persistent photoconductivity effect [7], which results in slow response times due to imperfect heterojunction interfaces [[8], [9], [10]].
For the GaN-based devices, controlling the GaN heterojunction is very important [11,12]. High-quality p-n GaN junctions with low interfacial strain and defect densities are difficult to obtain using traditional growth methods, and current fabrication techniques can damage the heterojunction interface. Thus, it is important to develop a simple and low-cost method to fabricate GaN-based devices [13,14]. Recently, NiO has been used to fabricate p-n junction detectors using ZnO and GaN [15,16]. The NiO nanostructures can effectively improve the device performance due to their high hole mobility [[17], [18], [19], [20]].
In this paper, we have fabricated a rapid-response p-GaN/NiO nanostructures/n-GaN sandwich structure detector which exhibited a high sensitivity, fast response, and rapid recovery time. It provides a method to fabricate high-response UV photodetectors for GaN-based materials by combining them with metal oxide nanostructures.
Section snippets
Experimental
Metal-organic chemical vapor deposition (MOCVD) was used to grow 2 μm GaN epilayers with different doping [16]. Trimethylgallium (TMGa) and ammonia (NH3) were used as the gallium and nitrogen precursors. Silane (SiH4) was used as n-type dopant and bicyclopenta-dienyl magnesium (CP2Mg) was used as the p-type dopant, respectively. The dopant concentrations were 5 × 1018 cm−3 for n-type and of 3.6 × 1017 cm−3 for p-GaN. To construct the sandwich-structured UV detector, NiO nanostructures were
Results and discussion
Fig. 1 demonstrates the XRD pattern of as-grown NiO nanostructures. The dominant peak is from n-GaN. And the other peaks corresponding to (111), (200) and (220) cubic-NiO planes, in agreement with JCPDS card No. 47–1049.
Fig. 2 shows FESEM images of the plane-view and cross-section of as-grown NiO nanostructures. The morphology of NiO nanostructure is displayed in Fig. 2(a). A sheet-like morphology can be clearly observed in the n-GaN surface. The thickness of the NiO layer is around 1.5 μm
Conclusions
A high-performance p-GaN/NiO nanostructures/n-GaN sandwich structure was obtained using a direct-contact method. The NiO nanosheet layer served as an electron blocking layer to decrease the dark current. Meanwhile, the unique sheet-like structure provided channels for electrons and holes which contributed to the fast response speed. The results may provide a new fabrication method for high-performance GaN-based UV photodetectors.
Declaration of interests
The authors declared that they have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.
Acknowledgments
This work was supported by LiaoNing Revitalization Talents Program (No.XLYC1807004), Chongqing Key Laboratory of Photo-Electric Functional Materials, Chongqing Normal University(201901), Open Foundation of Zhenjiang Key Laboratory for high technology research on marine functional films (ZHZ2019005), Guangxi Key Laboratory of Precision Navigation Technology and Application, Guilin University of Electronic Technology (No.DH201909).
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