Research On High-performance Photodetectors Based On Zinc Oxide Nanomaterials

Zinc oxide(ZnO)is a semiconductor material with wide bandgap and high physical and chemical stability and shows broad application in the field of ultraviolet(UV)photodetectors(PDs).However,ZnO-based UV PDs still have some shortcomings,such as slow response speed,low sensitivity,small signal-to-noise ratio(SNR)and complex preparation process.In this thesis,based on the preparation of ZnO materials with different microstructures,the effects of material properties and device structures on the PDs performance were systematically studied and also the response mechanism of detectors was further discussed,which provide theoretical and experimental supports for optimizing the response performance of ZnO-based PDs.The main achievements of this thesis are as follows:1.Fabrication and properties of ZnO-based films UV detectorsZnO thin films were deposited on quartz substrate using Sol-Gel method.The crystal structure,surface morphologies and optical properties of ZnO films were studied at different annealing temperatures(400°C,500°C and 600°C).Moreover,the response performance of PDs was also investigated.The results showed that PDs exhibit the best response properties at the annealing temperature of 600°C.Under the 3 V bias and 365nm UV light irradiation,the response time and recovery time of detector are 4.172 s and11.012 s,respectively.Furthermore,the detectivity,SNR and sensitivity of device are3.9×10~9 Jones,31.6 dB and 38.03,separately.On this basis,ZnO films were prepared by dip coating technology,and the effect of withdrawal speed on the response performance of PDs was studied.In order to decrease the dark current and improve SNR,a small amount of manganese nitrate solution(Mn/Zn=2.5 at.)was added to the precursor solution.The results showed that the device fabricated at 40 mm/s exhibits the best response performance under 3 V bias and 365 nm UV light irradiation and the response time and recovery time are 1.871 s and 3.309 s,respectively.Meanwhile,the formed detectivity,SNR and sensitivity of PDs are 3.9×10~9Jones,31.6 dB and 38.03,suggesting that the response performance of device can be effectively improved by changing the fabrication process.2.Fabrication and performance regulation of ZnO nanorods(NRs)arrays ultraviolet detectorsZnO NRs were grown on substrate using chemical bath deposition(CBD)method and then fabricating ZnO NRs-based UV PDs.The effect of precursor concentrations of sols on the response performance of PDs were systematically studied.The results showed that as the precursor concentration is 0.5 mol/L,the growth of ZnO NRs(hydrothermal condition:T=90°C for 3 h)exhibits the highest crystal quality and the largest aspect ratio of 14.69,which is much higher than the results reported by most researchers.Ultraviolet spectral response indicated that devices show higher responsivity in the range of 360-380nm.Under the 3 V bias and 370 nm UV light irradiation,ZnO NRs-based PDs fabricated at 0.5 mol/L show the highest response performance,and the sensitivity and SNR of device are 2348 and 67 dB.Also,response time and recovery time of PDs are 0.993 s and2.036 s,respectively.Compared with ZnO films,nanorods-based PDs show faster response speed,higher sensitivity and larger SNR.