MXene-GaN Van Der Waals Schottky Junction Based Multiple Quantum Well Photodetectors And Its Application

As one of the most important types of devices in photoelectric conversion,photodetectors are widely used in communication,sensing,imaging,data processing and many other fields.The future trends in information technology applications will develop towards ultra-high integration,ultra-high bandwidth,ultra-low delay and ultra-reliability,which will put forward higher requirements for photodetectors.Among all kinds of photodetectors,metal-semiconductor-metal(MSM)photodetectors are popular for their fast response,simple fabrication process and feasibility of integration with field effect transistor(FET)technology.However,the traditional manufacturing process of MSM photodetectors will produce chemical disorder and defect states at the metal-semiconductor interface,resulting in significant dark current and noise.In order to solve the problems above,this thesis studies the MXene-GaN Van der Waals Schottky junction based multiple quantum well photodetectors and its application.MXene(Ti₃C₂T_x),which is a two-dimensional material with metal conductivity,interacts with other bulk semiconductors with van der Waals force outside the atomic plane.Compared with the traditional MSM multiple quantum well photodetectors,the van der Waals Schottky junction formed between MXene and GaN has fewer defect states,and the Fermi pinning effect is marginal,therefore the performance of MXene-GaN-MXene multiple quantum well photodetectors is significantly improved.The research contents and results of this thesis are listed as follows:(1)Multiple GaN/In GaN quantum wells were grown on a patterned sapphire substrate by metal-organic chemical vapor deposition(MOCVD).Two dimensional Ti₃C₂T_x nanosheet solution was prepared by etching the MAX phase of Ti₃Al C₂.In order to verify the good interface between MXene and GaN,a planar MXene-GaN-MXene multi-quantum well photodetector was formed by directly depositing two-dimensional Ti₃C₂T_x onto the defect-sensitive GaN/In GaN quantum well surface using the cover-drop coating method.Experimental results show that compared with the traditional metal-gallium-nitride-metal multi-quantum well photodetector,the maximum responsivity of the proposed detector in blue and violet light band was improved by about one order of magnitude,reaching 64.6 A/W.Dark current dropped by three orders of magnitude;The specific detectivity increased by four orders of magnitude to 1.93×10¹² Jones.Thanks to the good interface between MXene and GaN,which enables the identification of photocurrent distribution with fine distinction of nanoamps in submicron scale,the local enhancement effect of patterned sapphire substrate on photocurrent extraction was observed.(2)In order to exhibit its good prospects in specific applications,this thesis designed and manufactured a small underwater optical wireless communication system and turbidity sensor system based on the MXene-GaN-MXene multi-quantum well photodetector.Compared with the control group based on the traditional MSM detector,the power consumption of the underwater optical wireless communication system was reduced by 3 orders of magnitude,and the high-frequency noise(20 k Hz-50 k Hz)was improved.The turbidity sensing system based on the proposed detector achieved a resolution of 100 NTU at turbidity higher than 3000 NTU,10 times higher than that of the control group,even with the single-channel sensing architecture.