The Study On ?-? Nanostructures Preparation And Optoelectronic Properties

Inthe past decades,InAs/GaSb based ?-?Semiconductor nanostructures has gain much attention due to its large Boer exciton radii and excellent photoelectric properties.At present,these materials were synthesized mainly through MOCVD and MBE.However,these methods have drawbacks due to high cost and highly toxic reaction residue,these factors limit the generalization of abovementioned methods.Inour work,we have synthesized several based ?-?Semiconductor nanostructures by employing the traditional CVD route,such as GaSb nanowires,quaternary Ga_xIn_1-xAs_1-ySb_y alloy nanowires with the composition are adjustable,GaInAsSb alloy nanosheets,and InAs/GaSb based lateral heterojunction.The morphology,composition and structure of the products were analyzed by SEM,TEM,Laser Raman spectrometer,XRD,STEM.Photoluminescence characterization was measured by Near-field optical microscopy and self-built infrared detection system.We employed the semiconductor parameter analyzer tested nanodevices which constructed by these nanostructures.Inaddition,through a improved CVD system,we have studied the collaboration and competition between VLS and VS mechanism and the deep mechanism of axial epitaxy and radial epitaxy of nanomaterials.Inthis paper,the following research results are obtained:?1?High-quality GaSb nanowires were synthesized by CVD route.Ina solid source evaporation reaction system,material growth conditions?temperature,pressure,?/? ratio,deposition temperature zone,etc?,will be greatly affected morphology and crystal quality of the products.Inour experiments,by gradually increasing the growth time of the GaSb powder,the length and diameter of GaSb nanowires increased uniformly.XRD patterns indicate that the prepared nanowires have excellent crystallinity,were the zinc blende structure.Laser Raman spectroscopy showed that,with the laser power increases,the TO-mode and LO-mode of the GaSb nanowires move in the low wavenu mber direction.Which is attributed to the laser heating effect and the phonon confinement effect in the testing process.Photoluminescence spectra show that GaSb nanowires emit light mainly from bandgap direct transition.Transistor test indicated that Th enanowire has a strong infrared light response.?2?Quaternary Ga_xIn_1-xAs_1-ySb_y alloy nanowires with the composition are adjustable were synthsised by CVD route.To a certain extent,this work have overcomed the mixed-band gap problem in quaternary alloy syst em.STEM structural characterization showed that the nanowires have excellent crystal quality. Photoluminescence spectra showed that the low-temperature photoluminescence of nanowires can be continuously adjusted from 1635 nm to 3250 nm.Using UV lithography and metal evaporation system,single-alloy nanowire transistors were fabricated,the response of peak R value and EQE can be achieved respectively 337 AW-1 and 4.0 2× 104 %.Combined with the motion equation of Maxwell 's gas molecule which based on near local quilibrium and ternary alloy phase diagram,we analyzed the formation mechanism of Ga_xIn_1-xAs_1-ySb_y quaternary alloy nanowires,as well as the realization of ?-?quaternary alloy system with all components continuous adjustment.?3?The GaInAsSb quaternary alloy nanosheets were synthesized by CVD method for the first time.STEM and XRD characterization showed that the nanosheets have high crystallization quality.Microdomain Raman spectroscopy showed that nanosheets exhibited multimode phonon vibrational behavior,with the increase in laser power,each branch mold moves to the low frequency band unanimously. It showed that phonon-confined effect was existd in this new quasi-one-dimensional material.Temperature-dependent photoluminescence data indicated that the thermal expansion factor ? of nanosheets is obviously lower than that of GaInAsSb thin films,this is due to the thermal expansion limit caused by the small size effect.Subsequently,we designed the infrared detection device based on single nanosheet,the test results showed that,the peak response R value of up to 675 A / W,the corresponding external quantum efficiency EQE value of 8.05 ×104%,which is much higher than that based on GaInAsSb thin films.Inaddition,combined with VLS and VS mechanism,the formation mechanism of nanosheets was analyzed.?4?GaSb/InAs-based transverse lamellar heterostructures were synthesized by CVD for the first time.The structure has a leaf-like morphology,STEM characterization indicated that the crystal structure wa s cubic phase,the growth direction of the stem portion and the growth direction of the patch region are perpendicular to each other.The appearance of this lamellar transverse heterostructure,mean that the extension of the heterostructure of III-V semiconductors was realized,and to a certain extent,the emergence of the bionicphenomenon of inorganic materials.Combined with nano-structured facet epitaxy mechanism and VLS,VS growth mechanism,the formation mechanism of GaSb / InAs-based transverse lamellar heterostructures is proposed.However,the theory is still incomplete.By means of an electron beam exposure system,we constructed nanodevice that based on single lateral heterojunction,and a model of the double-channel transistor device based on the structure is designed.