Controllable Synthesis And Performance Investigation Of High-Mobility ?-? Nanowires

In recent years,with the shrinking size of transistors,Moore's law has reached its limit,and the growth rate of chip integration density has slowed down.Therefore,it is proposed to continue Moore's law from the aspects of device integration and system function diversification.Among them,one of the effective solutions is to explore new channel materials with higher mobility and realize wrap-gated nanowire transistors.During the exploring of new channel materials with high mobility,?-? nanowires have been widely concerned.This paper focuses on the controllable synthesis and performance of high mobility ?-? nanowires.Firstly,this paper introduces one-dimensional inorganic nanowires.One-dimensional nanowires have excellent optical absorption ability,excellent carrier separation and collection ability,excellent mechanical flexibility,rich surface state control function and good compatibility.It has unique advantages in the research of the dimension dependence of electrical properties,photoelectric properties and mechanical properties,At the same time,by controlling size and composite structure,one-dimensional nanowires can be applied in the fields of electronics,magnetism,acoustics,photonics,etc.,to promote the continuation of Moore's law in the aspects of device integration and system function diversification.Among one-dimensional nano wires,?-?nanowires hold high carrier mobility,direct and narrow band gap,and strong radiation resistance.Therefore,the application of the field effect transistor,logic circuit,photodetector and solar cell of the ?-? nanowires,has become a new generation semiconductor for the application of nano electronic and optoelectronic devices.This paper elaborates the experimental methods and principles involved.Firstly,the growth methods of the ?-? semiconductor nanowires are introduced,including the"top-down" and "bottom-up" methods.The growth mechanisms of nanowires,including vapor-liquid-solid and vapor-solid-solid,are described.The technological conditions and parameters,including temperature and catalyst,etc.of the controllable growth of nanowires are introduced.Finally,the working principle,performance parameters and preparation methods of field effect transistor,the working principle and main performance parameters of photodetectors,the working principle and main performance parameters of complementary metal oxide semiconductor(CMOS)in verter are introduced.Compared with the theoretical high mobility of group ?-? materials,the low field effect mobility of group ?-? nanowires limits their development,which is mainly due to the uncontrollable surface state,crystal quality,and carrier concentration of nanowires.In particular,the mismatch of mobility between n-type and p-type devices limits the continuous miniaturization of modern electronic chips.Therefore,improving the mobility of ?-? nanowire field effect transistors will promote the further development of integrated circuits.The controllable synthesis,mobility enhancement and performance control of ?-? nanowires are essential,which are the focus of this paper.Carrier mobility mainly depends on the fabrication technology and channel semiconductors.Manufacturing technology is complex,and each process is important for the carrier mobility of the device.On the other hand,the carrier mobility can also be adjusted by changing the crystallinity,growth plane,carrier effective mass and carrier concentration of the channel semiconductor.By designing the crystal growth plane,we can control the polarity,carrier effective mass and surface scattering,to improve the mobility of field effect transistor.In this paper,ultra-high mobility field effect transistors are realized by controlling the carrier scattering and concentration of nanowires.One of the main works of this paper is to develop a new method for the growth of nanowires using solid-state catalysts.By controlling the crystal structure of the nanowires,the carrier lattice scattering effect is weakened,and the electron mobility of InP nanowires is increased to the theoretical value(2000 cm2·V-1·s-1).In addition,in modern electronic chips,the carrier mobility of p-channel devices is always lower than that of n-channel ones,which brings challenges to the continuous miniaturization of electronic and optoelectronic application.Therefore,in this paper,we have done in-depth research on p-type nanowires,take GaSb nanowire as an example.The second work is based on the intrinsic hole origin of GaSb,the theoretical design and realization of in-situ light doping of catalyst into nanowire's body,effectively weakens the Coulomb scattering effect of carriers,improves the hole mobility of GaSb nanowires to the theoretical value(1028 cm2·V-1·s-1),and shows excellent infrared detection ability.Finally,we developed a new method to control the field effect mobility by using metal-semiconductor junctions.The hole mobility of GaSb nanostructured field-effect transistors broke the theoretical value to 3372 cm2·V-1·s-1.The specific works are as follows:1.InP nanowires with electron mobility close to theoretical value are synthesized and studied in electrical and photoelectric properties.A new method of nanowires growth with solid-state catalyst is developed.The scattering of carrier lattice is weakened by controlling the crystal structure of nanowires,and the electron mobility of InP nanowires is increased to the theoretical value.InP nanowires,as an important semiconductor nanomaterial,have many defects(such as twin and mixed phase)in the typical vapor-liquid-solid growth mode,which leads to lower electron mobility and limits its practical application in the electronic field.To solve this problem,in chemical vapor deposition,the vapor-solid-solid growth mode is successfully realized by using Pd catalyst,which exhibits high melting point.The nonpolar-oriented and high-quality wurtzite InP nanowires are synthesized.The detailed relationship between growth characteristics,orientation uniformity and excellent crystallinity of InP nanowires is studied.The surface energy of solid Pdln catalysts with polyhedron shape under vapor-solid-solid growth mode is calculated.Specifically,Pdln solid catalyst particles exposed the Pdln{210} plane with the lowest energy at the nucleation interface of InP nanowires,which has the minimum lattice mismatch with the nonpolar InP{2110} and {1010} planes.Therefore,the appropriate lattice matching makes the highly crystallized InP nanowires grow in the nonpolar-orientation.Because of the good control of crystal defects and the weakening of the lattice scattering of carriers,InP nanowires have achieved a record high electron mobility of 2000 cm2·V-1·s-1,which is close to the theoretical value of bulk materials with the electron concentration is 1017 cm-3.The statistics on electron mobility is relatively high as 1000-2000 cm2·V·-1·s-1,which proves the feasibility of the method.At the same time,InP nanowire top gate field effect transistor is successfully prepared.The device shows very small subthreshold swing at room temperature,which is as low as 91 mV·dec-1.In addition,when the InP nanowires are applied to photodetectors,the responsivity is as high as 104 A·W-1(one of the highest values among all InP nanowires reported in the literature),and exhibits a fast rise and fall time of 0.89 s and 0.82 s.respectively.All of the results prove that the high-quality InP nanowires synthesized in this work have a very good application prospect in the future electronic and optoelectronics fields.2.GaSb nanowires with hole mobility reaching the theoretical value are synthesized and studied in electrical and photoelectric properties.Based on the origin of the intrinsic hole of GaSb,the light doping of catalyst into nanowires is designed and realized theoretically,which effectively weakened the Coulomb scattering of carriers,and the hole mobility of GaSb nanowires is increased to theoretical value.In this work,in order to solve the problem of limited application due to the low mobility of p-type GaSb nanowires,we first studied the controllable synthesis of GaAsSb nanowires.The high quality GaAsSb nanowires are grown by simple surfactant assisted chemical vapor deposition.The source quality and temperature are adjusted to regulate the composition,diameter and growth rate of the GaAsxSb1-x nanowires.Then the effects of As ratio on the electrical and infrared detection performance are studied.The results show that with the increase of As ratio,the field effect hole mobility of GaAsxSb1-x nanowires decreases gradually.The infrared detection performances of GaAsxSb1-x(x=0.6,0.26,0.5)nanowires are also studied.With the increase of As ratio,the photocurrent,responsivity and detectivity of GaAsxSb1-x nanowire infrared detectors decreased.Therefore,improving the hole mobility can improve the infrared detection performance of the GaSb nanowires.Next,the Coulomb scattering of carriers in GaSb nanowires is effectively weakened by the in-situ light doping method,and the theoretical value of hole mobility is realized.Firstly,the band structure,carrier effective mass and the formation energy of the system are simulated.The results show that the hole mobility of GaSb will be improved after Sn light doping.Therefore,in this work,the long,straight,uniform and high crystallinity GaSb nanowires are successfully synthesized by using surfactant assisted chemical vapor deposition method,and Sn as the catalyst and light doping source for nanowire growth.The hole mobility of the single nanowire back-gated field effect transistor is up to 1028 cm2·V-1·s-1,which reaches the theoretical value of GaSb hole mobility.On the other hand,the parallel array devices also show a peak hole mobility of 170 cm2·V-1·s-1.Through a variety of characterization,we find the reason of hole mobility reaches the theoretical value.The photoluminescence spectra of Sn-catalysed GaSb nanowires shows a red shift of 0.05 eV compared with Au-catalyzed nanowires.High resolution transmission electronmicroscopy result shows that the tip of catalyst can gradually diffusion into the nanowire's body during the growth process.At the same time,the energy spectrometer equipped with high resolution transmission electronmicroscopy detects the Sn signal,and the Sn signal peak existed in the radial etching nanowire tested by X-ray photoelectron spectroscopy.All these prove the uniform light doping of Sn in GaSb.Finally,the infrared detection performance of GaSb nanowires with hole mobility reaching theoretical value is studied.Under the irradiation of 1550 nm infrared light and 520 nm visible light,both the single nanowire devices and the nanowire array devices of GaSb have excellent photodetection performance,including the response time of hundreds of microseconds.Compared with the Au-catalyzed GaSb and GaAsSb nanowire infrared detectors,Sn light doped GaSb nanowire devices have faster response speed and higher responsivity and detectivity,which verifies that improving the hole mobility is helpful to improve the infrared detection performance of GaSb nanowires.In a word,the Sn light doped GaSb nanowires with the theoretical value of the hole mobility have a broad application prospect in the next generation electronics and photoelectrics.At the same time,employing suitable catalyst as the light doping origin for nanowire growth is a universal method,which provides reference for controllable synthesis of high-performance nanowires.3.Using metal-semiconductor junctions to further increase the field-effect hole mobility of GaSb nanowires.A new method of employing metal-semiconductor junction to control the mobility of nanowire field effect transistors is developed.The field-effect hole mobility of GaSb nanowire field effect transistor increases effectively.Among all III-V semiconductors,GaSb holds the highest hole mobility.The prevrous work has raised the hole mobility to theoretical value by weakening Coulomb scattering.However,in order to further improve the hole mobility of p-type semiconductor devices to reach the same level as that of n-type ones,CMOS-compatible metal particles with different work functions are deposited on the semiconductor surface to form a metal-semiconductor junction to regulate the hole concentration and electrical properties of p-type semiconductor field effect transistors in this work.When the low-power function metals Al,Sn and Ti are deposited,the peak hole mobility of GaSb nanowire field effect transistors is significantly increased,reaching 3372 cm2·V-1·s-1,1938 cm2·V-1·s-1 and 2840 cm2·V-1·s-1,respectively.After Al-GaSb junction is constructed,the peak hole mobility of GaSb nanowire field effect transistor is three times of the original value,which is the highest value of p-channel field effect transistor reported in the atmosphereat at room temperature.The significant increase of hole mobility is due to the decrease of hole concentration caused by the downward bending of energy band at the metal-semiconductor interface.At the same time,other important electronic characteristics of GaSb nanowire field effect transistor,such as threshold voltage and subthreshold swing,are also well-controlled.It is important that when combine p-type GaSb nanowire field effect transistor with n-type InGaAs nanowire field effect transistor,the CMOS inverter has good inverse characteristics and achieves relatively high gain of?8.1,which is benefit from the enhanced hole mobility and controllable threshold voltage and subthreshold swing.The method of using metal-semiconductor junction to regulate the field effect mobility of p-type materials is universal,and has been verified in other p-channel devices,such as p-GaAs nanowire field effect transistors,GaAs film field effect transistors and two-dimensional WSe2 field effect transistors.The thiner the thickness of channel materials,the more obvious the effect of hole mobility increases.The metal-semiconductor junction studied in this work can be regarded as an important progress to improve the hole mobility of p-channel devices and promote the development of next-generation electronic technology.In conclusion,the controllable synthesis of high mobility ?-? nanowires is studied in this paper.By adjusting the scattering and concentration of carriers in nanowires,InP nanowires with electron mobility close to theoretical value,GaSb nanowires with hole mobility reaches theoretical value,and GaSb nanowires with further increased field-effect hole mobility are studied.The electrical properties and photoelectric properties of these nanowires are studied.The relationship between the material mobility and infrared detection performance is further constructed,which is "high mobility is benefit to realize high-performance infrared detection".Based on the GaSb nanowire field effect transistors with the ultra-high field-effect hole mobility,the application of CMOS inverter is realized.The innovative and universal growth method of nanowires and the stratagies of improving the hole mobility of p-type materials proposed in this paper provide reference for the controllable synthesis and performance optim ization of high-performance nanowire devices.