Fabrication Of P-Si/V-doped ZnO Photodetectors And Study On Photoresponse Properties

At present,the emerging two-dimensional materials show great potential in the regulation and control of the photoelectric processes.However,there are few studies on ferroelectric two-dimensional materials.The ferroelectric material has spontaneous polarization and the direction of the spontaneous polarization can change with the direction of the external electric field.Its polarized charge will affect the energy band structure at the interface.Therefore,the ferroelectric two-dimensional materials have broad application prospects in optoelectronic devices,which will also bring potential functional characteristics combining with piezoelectric optoelectronic effects.In this thesis,vanadium-doped zinc oxide（V-ZnO）nanosheets were prepared by hydrothermal method and p-Si/V-ZnO heterojunction photodetector was fabricated.And the influence of ferroelectricity and ferroelectric coupling piezoelectric optoelectronics effect on the photoresponse performance of p-Si/V-ZnO photodetectors has been deeply studied.First,a ferroelectric V-ZnO nanosheet doped with 1 mmol%V was synthesized by hydrothermal method and a p-Si/V-ZnO photodetector was constructed.When the photodetector is irradiated by a 442 nm laser with the power density of 10 m W/cm²,under a forward bias voltage of+1 V,the photoresponsivity R of the photodetector under strain-free conditions is 61.6 m A/W;At-0.20‰compressive strain,the light response performance R increased to 120.3 m A/W.Under the same conditions,when a compressive strain of-0.20‰is applied,the photoresponsivity R of the p-Si/ZnO photodetector without ferroelectricity is only 35.1 m A/W.By introducing ferroelectric and piezoelectric optoelectronic effects,the rectification characteristics of the current can be improved,and the photoresponse performance of the heterojunction can be enhanced in a wider spectral range.In order to further enhance the ferroelectricity of V-ZnO nanosheets,the ferroelectric V-ZnO nanosheets doped with 2 mmol%V was synthesized and the p-Si/V-ZnO photodetector was fabricated.When compared with the non-ferroelectric p-Si/ZnO photodetector,the photoresponsivity R of the ferroelectricity p-Si/V-ZnO photodetector irradiated with 442 nm laser under the power density of 10 m W/cm²,is increased from 13 m A/W to 72.38 m A/W at+1 V bias,which is about 5.5 times higher.And the photoresponsivity R of the ferroelectricity p-Si/V-ZnO photodetector irradiated with 1064 nm laser under the power density of 3 m W/cm²,is increased from 70 m A/W to 828 m A/W at+1 V bias,which is about 12 times higher,comparing with the non-ferroelectric p-Si/ZnO photodetector.When the power density is 0.48 m W/cm²,the photoresponsivity R can reach a maximum value of 2.7 A/W,and D*can reach a maximum value of 9.4×10¹¹ Jones.Even at a bias voltage of-1 V,ferroelectricity can improve the photoresponse performance.The experimental results show that,due to the orderly arrangement of ferroelectric spontaneously polarized charges under the applied external electric field,V-ZnO nanosheets can directly and effectively modulate the energy band structure of the junction interface,thereby greatly improving the generation,separation and transmission efficiency of photogenerated electron-hole pairs.The feasibility of direct modulation of the energy band structure at the junction interface by ferroelectric spontaneous polarization is proved,which provides a new perspective for energy band engineering.