Innovative Research On ?-? Semiconductor Rolled-up 3D Structures And Related Typical Devices

Recently,the 3D assembly technologies and 3D structures or devices are of increasing interest and exbihit attractive applications.As the dimensions of devices are increased from conventional 2D to 3D,it is undoubted that the footprint of devices are reduced,as well as the integration density is significantly increased.The results effectively promote the development of microelectronic chip,artificial intelligence chip,optoelectronic integrated chip,data center,optical interconnection chip and so on.Furthermore,the 3D structures not only have varied spatial configurations,but also could be directly combined with functional materials or structure,which enhances the performance of devices and brings a variety of novel effects or functions.Thus,the 3D assembly technologies provide greater freedom in fabricating innovative devices.As one of 3D assembly technology,self-rolling technology makes the planar 2D structure into rolled-up 3D structure via releasing strain.The rolling mechanism is simple and compatibles with planar process.Moreover,this technology has high controllability/stability/repeatability,a wide range of rolling materials and easily incorporated with a variety of functional materials.Thus,it has great advantages over high integration-density,high-performance and arrayed optoelectronic devices.Thus,we achieve the high-performance controlled assembling of rolled-up 3D structures via ?-? group semiconductor self-rolling method.Then,the functional materials or structures are efficiently combined to systematically study rolled-up 3D lasers and photodetectors.The main as-obtained results are as following:1.We introduce the AlGaAs separate confine heterostucture(SCH)to embed the single layer of quantum dots into GaAs well from GaAs/AlGaAs quantum well,for the purpose of limiting carriers escape and enhancing the luminance of quantum dots.Next,the free-standing microtube with a diameter of?7.1 ?m is fabricated by using the U-shaped mesa and the whispering gallery modes(WGMs)are observed around 1.1?m after the measurement of confocal micro-photoluminescence system.It is demonstrated that the single layer of quantum dots rolled-up tubular microcavity with a factor of 1200 is successfully achieved,which is different from the previously reports about two layer of quantum dots rolled-up tubular microcavity.This work lays a solid foundation in optically pumped quantum dot microtube laser in the next step.2.We further innovatively research on rolled-up quantum dot tubular microcavity from the perspective of substrate and quantum dots active region,respectively.(2.1)Using liquid-assisted sub-on-sub transferring method,we transfer the GaAs-based non-free-standing InAs quantum dot microtube to SiO2(300nm)/Si substrate and successfully obtain the Si-based 1.3 ?m quantum dot tubular microcavity.Due to the low-refractive-index SiO2 layer greatly reduces substrate loss,the WGMs appear in the RT ?-PL spectrum of BQD microtube around 1.3 ?m with a factor of 1100.This work gives great help for Si-based micro/nano light sources.(2.2)Inspired by the ?-? group semiconductor self-assembled quantum dot tubular optical microcavity,we first present the design that optical microcavity is fabricated by embedding the colloidal quantum dots into self-rolled-up microtube wall and apply for a patent.This design avoids the disadvantage that self-assembly quantum dots can't cover the visible wavelength.Besides,it makes the quantum dots completely covered by the tube wall,which protects the quantum dots from the air and improves the coupling efficiency between the active region and microcavity.3.Based on the single layer of quantum dots rolled-up tubular microcavity,we present a novel design of lifting the self-rolled-up microtube with the support of Au pad,aiming to further separate the tube from GaAs substrate and decrease the substrate loss.As a result,we achieve an optically pumped laser with a threshold of?4?W at room temperature by using the combination design of "AlGAs SCH layer”and"Au pad".4.Combining the ?-? group InGaAs/GaAs self-rolled-up microtube and graphene,we fabricate the novel tubular 3D hybrid functionalized structures,paying a way for 3D photoelectric devices.(4.1)We achieve the assembly of reduced oxide graphene(RGO)and rolled-up InGaAs/GaAs mircrotubes,which offers the key 3D InGaAs/GaAs/RGO hererostructures for rolled-up 3D optoelectronic devices.Specifically,we first coat the graphene oxide(GO)layers onto the InGaAs/GaAs strained mesas.Then,the GO layers are reduced into RGO layers after annealing.Finally,the RGO layers and InGaAs/GaAs mesas are rolled into tubular structures(i.e.,InGaAs/GaAs/RGO hybrid microtubes)by undercutting the AlAs sacrificial layers.We study the relationship between the Raman characteristic peaks and three typical rolling behaviors via Raman tools.This work is helpful to further know the rolling behaviors for InGaAs/GaAs/RGO hybrid membranes.(4.2)We present a design of combining the CVD graphene and holey rolled-up microtube and perform corresponding experimental verifications.Through transferring the CVD graphene on the holey InGaAs/GaAs mesas,the functionalized rolled-up structures are fabricated after triggering the rolling mechanism,which have wide application in the filed of micro fluid,cell culture and so on.Besides,the holes on the rolled-up microtube make the graphene suspended to avoid the influence of substrate,enhancing the performance of devices.5.Based on the as-obtained semiconductor/graphene heterostructure,we first present the design of rolled-up 3D semiconductor/graphene heterojunction photodetector and then fabricate the device in experiments.It has great potentials in self-driven,omnidirectional,high-performance photodetector.Inspired by the aforementioned the design of lifting the tube by Au pad,we skillfully set two edge electrodes and a middle electrode,which solves the contact problem between the rolled-up tubular heterostructure and metal electrodes.The current-voltage(?-?)curve under dark environment shows an obvious rectifying behavior.When the incident light is?264 ?W at a bias voltage of 0V,the time-current(I-T)curve shows a dark current of 8× 10-12 A,a photocurrent of 1.6×10-7 A and thus the on/off ratio is 2×104,demonstrating that the as-fabricated device has obvious photovoltaic effect.