Research On Self-rolled-up Tubular Semiconductor Functional Structures

With the rapid development of the information society and the vigorous implementation of the "Internet +" strategy in China,the emerging of Internet of Things,big data,cloud computing,artificial intelligence and other emerging technologies has directly brought about the breakthrough and great changes in the traditional industries.Human society is about to enter the real data era.The massive data transmission,exchange,processing,and storage generated by it will put forward higher and more demanding requirements on the volume,power consumption,and cost of the devices.Under this background,the miniaturization and integration of optoelectronics devices has become a general trend;In addition,with the development and maturity of the Internet of Things industry,human society is also entering the era of interconnection of everything.Smart interconnection,smart manufacturing,smart driving,smart home,smart medical care,smart pension and other concepts and applications emerge in an endless stream.People also need devices with IntelliSense capabilities.The semiconductor microtube manufactured by self-rolled-up micro/nano technology is a three-dimensional micro/nano tubular functional structure with a micro/nano scale,which plays an important role in device miniaturization and integration.It has been applied in integrated circuits,optoelectronic integration and other fields.It also has a hollow tubular structure.As a result,it can serve as an excellent fluid channel,can form an optical resonant cavity,and can be filled with smart sensor material.Thus,it is widely used in the field of smart sensing micro/nanometer sensing and microfluidic system.Using self-rolled-up semiconductor microtubes to fabricate high-quality whispering gallery mode(WGM)microcavities,thereby realizing low-power and high-stability microtube lasers,is of great significance for solving the biggest technical bottleneck in optoelectronic integration and practical application of optical data interconnections.The introduction of a low-dimensional heterostructure into the microtube optical microcavity as a gain medium can significantly increase the critical performance of the optical microcavity and the microtube laser,and therefore has received great attention from researchers.Based on the effect of the refractive index change on the resonant mode of the WGM,the obtained microtube optical microcavity can also be applied to the sensor device.Further,combining the microtube and the nanosensing functional material,sensor devices based on tubular fluid channels can be fabricated.The combination can expand the sensing mechanism of the microtube sensor and its application range.Therefore,in this dissertation,self-rolled-up InGaAs/GaAs microtube microtube was combined with self-organized InAs QDs and graphene,respectively.Related researches were also carried out.These works expand the application of semiconductor self-rolled-up microtubes.The relevant research work that the paper has carried out and the results achieved are as follows:1.Based on microtube with a single-layer InAs QDs embedded in the tube wall,an optical resonantor on Si were successfully fabricated,and WGM wree observed at a low temperature of 80K.The prepared GaAs-based microtubes with single-layer InAs QDs were transferred to a low-refractive-index Si-based SiOx substrate by an ethanol-assisted transfer method,and a Si-based WGM optical microcavity was successfully fabricated.The quality factor measured at 80K by a micro-area light fluorescence spectrometer was around 700(no resonance mode was observed at room temperature).Afterwards,the U-shaped tearing method was adopted to introduce a sinusoidal pattern on the outer edge of the self-rolled-up QDs microtubes to form an axial confinement,and finally the quality factor of the Si-based optical microcavity was increased from around 700 to about 1100(80K).2.After introducing the AlGaAs confining layers,the WGM of the Si-based QDs microtube resonantor was observed at room temperature.The upper and lower AlGaAs confining layers were introduced into the epitaxial structure of QDs microtube.After the transfer process,the WGM was successfully observed at room temperature.The highest quality factor was around 550.The photoluminescence spectra of Si-based QD microtube optical resonators with AlGaAs confining layers and without AlGaAs confining layerswere compared at low temperature(80K).It was found that the AlGaAs confining layers can effectively confine the carriers of InAs QDs.As a result,the photoluminescence intensity of QDs has increased by an order of magnitude,and the WGM has become clearer.This work has laid an important foundation for the subsequent preparation of Si-based microtube light source.3.It is found that the III-V semiconductor microtube optical resonator has good temperature stabilityIn the temperature range of 80-280K(40K temperature interval),the WGM of the Si-based QDs microtube with AlGaAs confining layers was measured at different temperatures.The experimental results showed that the temperature increase per 100K only leads to the red shifts 2.65nm and 2.3nm of the two major modes,indicating that the optical resonator has excellent temperature stability.The experimental data is very close to the peak redshift(4.25 nm)calculated by the semi-quantitative method.This part of the research results is of great significance for the application of high-refractive index(3+)microtube sensors based on ?-? semiconductor materials.4.The tubular graphene was successfully fabricated by the micro/nano self-rolled-up technology.The strain regulation of tubular graphene was realized.Based on this,a tubular graphene gas sensor was designedGraphene produced by chemical vapor deposition(CVD)method was transferred to GaAs-based and Si-based InGaAs/GaAs strained double-layer,and then microtubes with diameters of 4.7?m and 3.7?m were fabricated by a strain-driven micro/nano self-rolled-up process.The high-quality tubular graphene tightly attached to the wall of the InGaAs/GaAs self-rolled-up microtube.It was found that after rolled up,the CVD graphene changes from unstrained to obvious tensile strained,and the strain comes from the GaAs layer;changing the diameter of the microtube can effectively regulate the strain state of the tubular graphene:the tensile strain of rolled-up graphene increase with the decrement of microtube diameter.Based on this,a novel microtube gas sensor with graphene gas sensing unit built-in was designed and preliminary feasibility experiment of the fabrication process was carried out.This part of the work provides a simple and flexible solution for the fabrication of strained rolled-up graphene,and extends the application of micro/nano self-rolled-up technology.