Preparation And Photoelectric Properties Of ZnO/Si Heterojunction With Complex Interfacial Structure

Zinc oxide(ZnO)is the II-VI compound semiconductor with wide direct bandgap(～3.37 e V),large exciton binding energy(～60 me V),good chemical and thermal stability.Therefore,it is expected to play an important role in the field of short-wavelength photodetection.The strong self-compensating effect of ZnO makes n-ZnO easy to obtain,and stable and controllable p-ZnO is difficult to achieve,which has also become one of the difficulties in constructing high-performance and stable ZnO photodetector.The single crystal silicon has good thermal conductivity and electrical conductivity,mature processing technology,easy realization of large-scale substrates at low cost,which makes silicon ideal p-type material for building ZnO heterojunction photodetector.However,there are still some problems to be solved for silicon-based ZnO photodetector:(1)Silicon is the indirect band gap semiconductor with a narrow forbidden band.The silicon-based planar heterojunction has a large light reflectivity,and the optoelectronic devices prepared on this basis have low light absorption;(2)There is a large lattice mismatch and thermal mismatch between bulk silicon and ZnO,and it is easy to generate large interfacial stress during the preparation process,which reduces the growth quality of the film and affects the device performance.For the above problems,this paper intends to prepare ZnO/Si-NPA non-planar heterostructure and construct ZnO/Si-NPA ultraviolet(UV)photodetector by using silicon nanoporous pillar array(Si-NPA)with non-planar patterned micro-nano structure as p-type substrate.Si-NPA has a triple hierarchical structure,namely:a regular array structure composed of micron-sized silicon pillar,a nanoporous structure of the silicon pillar,and silicon nanoparticles composing the nanopore pore wall.Based on the structural characteristics of Si-NPA,the preparation of ZnO/Si heterojunction with Si-NPA as the substrate has the following advantages:(1)The non-planar array structure and nanoporous structure of Si-NPA can effectively improve the light absorption ability;(2)The small size of silicon nanograins will lead to the broadening of the forbidden band width and the transformation from the indirect band gap to the quasi-direct band gap,which shows the unique optoelectronic properties;(3)The micro-nano-structured Si-NPA is used as the substrate,which can effectively reduce the interfacial stress generated during the deposition of the ZnO thin film through three-dimensional stress release,and improve the quality and heterojunction performance of the thin film.In this paper,the ZnO/Si-NPA heterojunction is prepared by magnetron sputtering method using Si-NPA as the substrate,and the UV photodetector based on ZnO/Si-NPA is constructed.The main results of the study are as follows:(1)ZnO/Si-NPA heterojunction were fabricated by magnetron sputtering method using Si-NPA as substrate.By studying and analyzing the effects of magnetron sputtering parameters such as substrate temperature,power and pressure on the quality and properties of ZnO thin films,the optimized preparation process of ZnO thin films was obtained.(2)Through the characterization and analysis of the surface and interface morphology,structure and composition of the ZnO/Si-NPA heterojunction,a physical model of the ZnO/Si-NPA heterojunction with complex interface structure was established,and its electrical properties and transport mechanism were analyzed.(3)The UV photodetector based on ZnO/Si-NPA heterojunction with complex interface structure was constructed.The test results show that under zero bias and 360nm UV light irradiation,the responsivity and specific detectivity of the device reach0.127 m A/W and 3.06×10~8 Jones,respectively,and the response and recovery times are 49 ms and 51 ms,respectively.ZnO/SNPA heterojunction with complex interfacial structure was constructed by using Si-NPA with micro-nano patterned structure as the substrate can effectively increase the light absorption rate of the device,shorten the transmission distance of photogenerated carriers,and improve the current carrying capacity.It is an effective way to fabricate ZnO/Si heterojunction ultraviolet photodetectors.