Modulation of the Schottky barrier heights was successfully demonstrated for WNx/p-Ge and WNx/n-Ge contacts by increasing the nitrogen component in the WNx films. The WN0.38/p-Ge contact exhibits rectifying characteri...Modulation of the Schottky barrier heights was successfully demonstrated for WNx/p-Ge and WNx/n-Ge contacts by increasing the nitrogen component in the WNx films. The WN0.38/p-Ge contact exhibits rectifying characteristic and an apparent Schottky barrier of 0.49 eV while the WN0.38/n-Ge Schottky contact exhibits quasi-Ohmic current–voltage characteristics. Dipoles formed at the contact interface by the difference of the Pauling electronegativities of Ge and N are confirmed to alleviate the Fermi-level pinning effect.展开更多
This paper reports that the Schottky barrier height modulation of NiSi/n-Si is experimentally investigated by adopting a novel silicide-as-diffusion-source technique, which avoids the damage to the NiSi/Si interface i...This paper reports that the Schottky barrier height modulation of NiSi/n-Si is experimentally investigated by adopting a novel silicide-as-diffusion-source technique, which avoids the damage to the NiSi/Si interface induced from the conventional dopant segregation method. In addition, the impact of post-BF2 implantation after silicidation on the surface morphology of Ni silicides is also illustrated. The thermal stability of Ni silicides can be improved by silicide- as-diffusion-source technique. Besides, the electron Schottky barrier height is successfully modulated by 0.11 eV at a boron dose of 1015 cm-2 in comparison with the non-implanted samples. The change of barrier height is not attributed to the phase change of silicide films but due to the boron pile-up at the interface of NiSi and Si substrate which causes the upward bending of conducting band. The results demonstrate the feasibility of novel silicide-as-diffusion-source technique for the fabrication of Schottky source/drain Si MOS devices.展开更多
A possible relationship between Schottky barrier heights and adhesion energies of different nonreactivemetal/semiconductor or insulator interfaces is presented .Various experimental evidences further sup-porting such ...A possible relationship between Schottky barrier heights and adhesion energies of different nonreactivemetal/semiconductor or insulator interfaces is presented .Various experimental evidences further sup-porting such a relationship are briefly exploited. The consequence indicated by such a relationship on the understanding of metal / ceramic interfaces is stressed.展开更多
We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co_2MnSi and the germanium（Ge） channel modulates the Schottky barrier height and the resistance–area product of the spin diode. W...We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co_2MnSi and the germanium（Ge） channel modulates the Schottky barrier height and the resistance–area product of the spin diode. We confirm that the Fermi level is depinned and a reduction in the electron Schottky barrier height（SBH） occurs following the insertion of the graphene layer between Co_2MnSi and Ge. The electron SBH is modulated in the 0.34 eV–0.61 eV range. Furthermore,the transport mechanism changes from rectifying to symmetric tunneling following the insertion. This behavior provides a pathway for highly efficient spin injection from a Heusler alloy into a Ge channel with high electron and hole mobility.展开更多
Ultra thin epitaxial CoSi 2 films are fabricated by solid state reaction of a deposited bilayer of Co(3nm)/Ti (1nm) on n Si(100) substrates at different temperatures.The local barrier heights of the CoSi 2/Si cont...Ultra thin epitaxial CoSi 2 films are fabricated by solid state reaction of a deposited bilayer of Co(3nm)/Ti (1nm) on n Si(100) substrates at different temperatures.The local barrier heights of the CoSi 2/Si contacts are determined by using the ballistic electron emission microscopy (BEEM) and its spectroscopy (BEES) at low temperature.For CoSi 2/Si contact annealed at 800℃,the spatial distribution of barrier heights,which have mean barrier height of 599meV and a standard deviation of 21meV,obeys the Gaussian Function.However,for a sample that is annealed at 700℃,the barrier heights of it are more inhomogenous.Its local barrier heights range from 152meV to 870meV,which implies the large inhomogeneity of the CoSi 2 film.展开更多
Reducing the Schottky barrier height(SBH)and even achieving the transition from Schottky contacts to Ohmic contacts are key challenges of achieving high energy efficiency and high-performance power devices.In this pap...Reducing the Schottky barrier height(SBH)and even achieving the transition from Schottky contacts to Ohmic contacts are key challenges of achieving high energy efficiency and high-performance power devices.In this paper,the modulation effects of biaxial strain on the electronic properties and Schottky barrier of Mo Si_(2)N_(4)(MSN)/graphene and WSi_(2)N_(4)(WSN)/graphene heterojunctions are examined by using first principles calculations.After the construction of heterojunctions,the electronic structures of MSN,WSN,and graphene are well preserved.Herein,we show that by applying suitable external strain to a heterojunction stacked by MSN or WSN—an emerging two-dimensional(2D)semiconductor family with excellent mechanical properties—and graphene,the heterojunction can be transformed from Schottky ptype contacts into n-type contacts,even highly efficient Ohmic contacts,making it of critical importance to unleash the tremendous potentials of graphene-based van der Waals(vd W)heterojunctions.Not only are these findings invaluable for designing high-performance graphene-based electronic devices,but also they provide an effective route to realizing dynamic switching either between n-type and p-type Schottky contacts,or between Schottky contacts and Ohmic contacts.展开更多
Fundamentals of the Schottky contacts and the high-temperature current conduction through three kinds of Schottky diodes are studied. N-Si Schottky diodes, GaN Schottky diodes and AlGaN/GaN Schottky diodes are investi...Fundamentals of the Schottky contacts and the high-temperature current conduction through three kinds of Schottky diodes are studied. N-Si Schottky diodes, GaN Schottky diodes and AlGaN/GaN Schottky diodes are investigated by I-V-T measurements ranging from 300 to 523 K. For these Schottky diodes, a rise in temperature is accompanied with an increase in barrier height and a reduction in ideality factor. Mechanisms are suggested, including thermionic emission, field emission, trap-assisted tunnelling and so on. The most remarkable finding in the present paper is that these three kinds of Schottky diodes are revealed to have different behaviours of high-temperature reverse currents. For the n-Si Schottky diode, a rise in temperature is accompanied by an increase in reverse current. The reverse current of the GaN Schottky diode decreases first and then increases with rising temperature. The AlGaN/GaN Schottky diode has a trend opposite to that of the GaN Schottky diode, and the dominant mechanisms are the effects of the piezoelectric polarization field and variation of two-dimensional electron gas charge density.展开更多
Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as...Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an A1GaN/GaN diode by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostrncture results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an A1GaN/GaN diode.展开更多
Schottky-contacted sensors have been demonstrated to show high sensitivity and fast response time in various sensing systems.In order to improve their sensing performance,the Schottky barriers height(SBH)at the interf...Schottky-contacted sensors have been demonstrated to show high sensitivity and fast response time in various sensing systems.In order to improve their sensing performance,the Schottky barriers height(SBH)at the interface of semiconductor and metal electrode should be adjusted to appropriate range to avoid low output or low sensitivity,which was induced by excessively high or low SBH,respectively.In this work,a simple and effective SBH tuning method by triboelectric generator(TENG)is proposed,the SBH can be effectively lowered by voltage pulses generated by TENG and gradually recover over time after withdrawing the TENG.Through combining the TENG treatment with piezotronic effect,a synergistic effect on lowering SBH was achieved.The change of SBH is increased by 3.8 to 12.8 times,compared with dependent TENG treatment and piezotronic effect,respectively.Furthermore,the recovery time of the TENG-lowered SBH can be greatly shortened from 1.5 h to 40 s by piezotronic effect.This work demonstrated a flexible and feasible SBH tuning method,which can be used to effectively improve the sensitivity of Schottky-contact sensor and sensing system.Our study also shows great potential in broadening the application scenarios of Schottky-contacted electronic devices.展开更多
The thermodynamic adhesion between a metal and a ceramic crystal was believed to be the result of theelectron transfer from the metal into the cerainic crystal. From an electronic point of view, such an electrontransf...The thermodynamic adhesion between a metal and a ceramic crystal was believed to be the result of theelectron transfer from the metal into the cerainic crystal. From an electronic point of view, such an electrontransfer at the metal/ceramic interface may be represented by the tunnelling of the metal conduction electron into the ceramic bandgap. Theoretical analysis of the quantum tunnelling process at an intimate rnetal-semicon-ductor contact were performed . and the relationship between adhesion energies and Schottky barrier heights ofvarious metal/semiconductor or insulator interfaces was dcduced .展开更多
The electrical characteristics of graphene Schottky contacts formed on undoped GaN semiconductors were investigated. Excellent rectifying behavior with a rectification ratio of -10^7 at ±2 V and a low reverse lea...The electrical characteristics of graphene Schottky contacts formed on undoped GaN semiconductors were investigated. Excellent rectifying behavior with a rectification ratio of -10^7 at ±2 V and a low reverse leakage current of 1.0 × 10^-8 A/cm^2 at -5 V were observed. The Schottky barrier heights, as determined by the thermionic emission model Richardson plots, and barrier inhomogeneity model, were 0.90, 0.72, and 1.24 ± 0.13 eV, respectively. Despite the predicted low barrier height of -0.4 eV at the graphene-GaN interface, the formation of excellent rectifying characteristics with much larger barrier heights is attributed to the presence of a large number of surface states （1.2 x 1013 states/cm2/eV） and the internal spontaneous polarization field of GaN, resulted in a significant upward surface band bending or a bare surface barrier height as high as of 2.9 eV. Using the S parameter of 0.48 （measured from the work function dependence of Schottky barrier height） and the mean barrier height of 1.24 eV, the work function of graphene in the Au/graphene/GaN stack could be approximately estimated to be as low as 3.5 eV. The obtained results indicate that graphene is a promising candidate for use as a Schottky rectifier in GaN semiconductors with n-type conductivity.展开更多
Transition metal dichalcogenides(TMDCs)are promising high performance electronic materials due to their interesting semiconductor properties.However,it is acknowledged that the effective electrical contact between TMD...Transition metal dichalcogenides(TMDCs)are promising high performance electronic materials due to their interesting semiconductor properties.However,it is acknowledged that the effective electrical contact between TMDCs-layered materials and metals remains one of the major challenges.In this work,the homogeneous monolayer MoS_(2)films with high crystalline quality were prepared by chemical vapor deposition method on SiO2/Si substrates.The back-gate field-effect transistors(FETs)were fabricated by inserting an ultrathin Al_(2)O_(3)interlayer between the metal electrodes and MoS_(2)nanosheets.With the addition of an ultrathin 0.8 nm Al_(2)O_(3)interlayer,the contact resistance decreased dramatically from 59.9 to 1.3 kΩμm and the Schottky barrier height(SBH)dropped from 102 to 27 meV compared with devices without the Al_(2)O_(3)interlayer.At the same time,the switching ratio increased from~106to~108,and both the on-current and field-effect mobility were greatly improved.We find that the ultrathin Al_(2)O_(3)interlayer can not only reduce the SBH to alleviate the Fermi level pinning phenomenon at the interface,but also protect the channel materials from the influence of air and moisture as a covering layer.In addition,the lattice and band structures of Al_(2)O_(3)/MoS_(2)film were calculated and analyzed by first-principles calculation.It is found that the total density of states of the Al_(2)O_(3)/MoS_(2)film exhibits interfacial polarized metals property,which proves the higher carrier transport characteristics.FETs with Al_(2)O_(3)interlayers have excellent stability and repeatability,which can provide effective references for future low power and high performance electronic devices.展开更多
The Schottky contact which is a crucial interface between semiconductors and metals is becoming increasingly significant in nano-semiconductor devices. A Schottky barrier, also known as the energy barrier, controls th...The Schottky contact which is a crucial interface between semiconductors and metals is becoming increasingly significant in nano-semiconductor devices. A Schottky barrier, also known as the energy barrier, controls the depletion width and carrier transport across the metal–semiconductor interface.Controlling or adjusting Schottky barrier height(SBH) has always been a vital issue in the successful operation of any semiconductor device. This review provides a comprehensive overview of the static and dynamic adjustment methods of SBH, with a particular focus on the recent advancements in nanosemiconductor devices. These methods encompass the work function of the metals, interface gap states,surface modification, image-lowering effect, external electric field, light illumination, and piezotronic effect. We also discuss strategies to overcome the Fermi-level pinning effect caused by interface gap states, including van der Waals contact and 1D edge metal contact. Finally, this review concludes with future perspectives in this field.展开更多
Phosphorene has attracted much attention recently as an alternative channel material in nanoscale electronic and optoelectronic devices due to its high carrier mobility and tunable direct bandgap. Compared with monola...Phosphorene has attracted much attention recently as an alternative channel material in nanoscale electronic and optoelectronic devices due to its high carrier mobility and tunable direct bandgap. Compared with monolayer （ML） phosphorene, few-layer （FL） phosphorene is easier to prepare, is more stable in experiments, and is expected to form a smaller Schottky barrier height （SBH） at the phosphorene-metal interface. Using ab initio electronic structure calculations and quantum transport simulations, we perform a systematic study of the interfacial properties of three-layer （3L） phosphorene field effect transistors （FETs） contacted with several common metals （A1, Ag, Au, Cu, Ti, Cr, Ni, and Pd） for the first time. The SBHs obtained in the vertical direction from projecting the band structures of the 3L phosphorene-metal systems to the left bilayer （2L） phosphorenes are comparable with those obtained in the lateral direction from the quantum transport simulations for 2L phosphorene FETs. The quantum transport simulations for the 3L phosphorene FETs show that 3L phosphorene forms n-type Schottky contacts with electron SBHs of 0.16 and 0.28 eV in the lateral direction, when Ag and Cu are used as electrodes, respectivel~ and p-type Schottky contacts with hole SBHs of 0.05, 0.11, 0.20, 0.30, 0.30, and 0.31 eV in the lateral direction when Cr, Pd, Ni, Ti, AI, and Au are used as electrodes, respectively. The calculated polarity and SBHs of the 3L phosphorene FETs are generally in agreement with the available experiments.展开更多
By means of analyzing theⅠ-Ⅴcharacteristic curve of NiSi/n-Si Schottkyjunction diodes（NiSi/n-Si SJDs）, abstracting the effective Schottky barrier height（φ_（B,eff）） and the idealfactor ofNiSi/n-Si SJDs and mea...By means of analyzing theⅠ-Ⅴcharacteristic curve of NiSi/n-Si Schottkyjunction diodes（NiSi/n-Si SJDs）, abstracting the effective Schottky barrier height（φ_（B,eff）） and the idealfactor ofNiSi/n-Si SJDs and measuring the sheet resistance of NiSi films（R_（NiSi））,we study the effects of different dopant segregation process parameters,including impurity implantation dose,segregation annealing temperature and segregation annealing time,on theφ_（B,eff） of NiSi/ n-Si SJDs and the resistance characteristic of NiSi films.In addition,the changing rules ofφ_（B,eff） and R_（NiSi） are discussed.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61176092 and 61474094)the National Basic Research Program of China(Grant Nos.2012CB933503 and 2012CB632103)the National Natural Science Foundation of China–National Research Foundation of Korea Joint Research Project(Grant No.11311140251)
文摘Modulation of the Schottky barrier heights was successfully demonstrated for WNx/p-Ge and WNx/n-Ge contacts by increasing the nitrogen component in the WNx films. The WN0.38/p-Ge contact exhibits rectifying characteristic and an apparent Schottky barrier of 0.49 eV while the WN0.38/n-Ge Schottky contact exhibits quasi-Ohmic current–voltage characteristics. Dipoles formed at the contact interface by the difference of the Pauling electronegativities of Ge and N are confirmed to alleviate the Fermi-level pinning effect.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60625403, 60806033, 90207004)the State Key Development Program for Basic Research of China (Grant No 2006CB302701)the NCET Program
文摘This paper reports that the Schottky barrier height modulation of NiSi/n-Si is experimentally investigated by adopting a novel silicide-as-diffusion-source technique, which avoids the damage to the NiSi/Si interface induced from the conventional dopant segregation method. In addition, the impact of post-BF2 implantation after silicidation on the surface morphology of Ni silicides is also illustrated. The thermal stability of Ni silicides can be improved by silicide- as-diffusion-source technique. Besides, the electron Schottky barrier height is successfully modulated by 0.11 eV at a boron dose of 1015 cm-2 in comparison with the non-implanted samples. The change of barrier height is not attributed to the phase change of silicide films but due to the boron pile-up at the interface of NiSi and Si substrate which causes the upward bending of conducting band. The results demonstrate the feasibility of novel silicide-as-diffusion-source technique for the fabrication of Schottky source/drain Si MOS devices.
文摘A possible relationship between Schottky barrier heights and adhesion energies of different nonreactivemetal/semiconductor or insulator interfaces is presented .Various experimental evidences further sup-porting such a relationship are briefly exploited. The consequence indicated by such a relationship on the understanding of metal / ceramic interfaces is stressed.
基金Project supported by the National Natural Science Foundation of China(Grant No.61504107)the Fundamental Research Funds for the Central Universities,China(Grant Nos.3102014JCQ01059 and 3102015ZY043)
文摘We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co_2MnSi and the germanium（Ge） channel modulates the Schottky barrier height and the resistance–area product of the spin diode. We confirm that the Fermi level is depinned and a reduction in the electron Schottky barrier height（SBH） occurs following the insertion of the graphene layer between Co_2MnSi and Ge. The electron SBH is modulated in the 0.34 eV–0.61 eV range. Furthermore,the transport mechanism changes from rectifying to symmetric tunneling following the insertion. This behavior provides a pathway for highly efficient spin injection from a Heusler alloy into a Ge channel with high electron and hole mobility.
文摘Ultra thin epitaxial CoSi 2 films are fabricated by solid state reaction of a deposited bilayer of Co(3nm)/Ti (1nm) on n Si(100) substrates at different temperatures.The local barrier heights of the CoSi 2/Si contacts are determined by using the ballistic electron emission microscopy (BEEM) and its spectroscopy (BEES) at low temperature.For CoSi 2/Si contact annealed at 800℃,the spatial distribution of barrier heights,which have mean barrier height of 599meV and a standard deviation of 21meV,obeys the Gaussian Function.However,for a sample that is annealed at 700℃,the barrier heights of it are more inhomogenous.Its local barrier heights range from 152meV to 870meV,which implies the large inhomogeneity of the CoSi 2 film.
基金Project supported by the Industry and Education Combination Innovation Platform of Intelligent Manufacturing and Graduate Joint Training Base at Guizhou University,China(Grant No.2020-52000083-01-324061)the National Natural Science Foundation of China(Grant No.61264004)the High-level Creative Talent Training Program in Guizhou Province,China(Grant No.[2015]4015)。
文摘Reducing the Schottky barrier height(SBH)and even achieving the transition from Schottky contacts to Ohmic contacts are key challenges of achieving high energy efficiency and high-performance power devices.In this paper,the modulation effects of biaxial strain on the electronic properties and Schottky barrier of Mo Si_(2)N_(4)(MSN)/graphene and WSi_(2)N_(4)(WSN)/graphene heterojunctions are examined by using first principles calculations.After the construction of heterojunctions,the electronic structures of MSN,WSN,and graphene are well preserved.Herein,we show that by applying suitable external strain to a heterojunction stacked by MSN or WSN—an emerging two-dimensional(2D)semiconductor family with excellent mechanical properties—and graphene,the heterojunction can be transformed from Schottky ptype contacts into n-type contacts,even highly efficient Ohmic contacts,making it of critical importance to unleash the tremendous potentials of graphene-based van der Waals(vd W)heterojunctions.Not only are these findings invaluable for designing high-performance graphene-based electronic devices,but also they provide an effective route to realizing dynamic switching either between n-type and p-type Schottky contacts,or between Schottky contacts and Ohmic contacts.
基金Project supported by the Foundation of Key Laboratory of General Armament Department, China (Grant No 5132030102QT0101)
文摘Fundamentals of the Schottky contacts and the high-temperature current conduction through three kinds of Schottky diodes are studied. N-Si Schottky diodes, GaN Schottky diodes and AlGaN/GaN Schottky diodes are investigated by I-V-T measurements ranging from 300 to 523 K. For these Schottky diodes, a rise in temperature is accompanied with an increase in barrier height and a reduction in ideality factor. Mechanisms are suggested, including thermionic emission, field emission, trap-assisted tunnelling and so on. The most remarkable finding in the present paper is that these three kinds of Schottky diodes are revealed to have different behaviours of high-temperature reverse currents. For the n-Si Schottky diode, a rise in temperature is accompanied by an increase in reverse current. The reverse current of the GaN Schottky diode decreases first and then increases with rising temperature. The AlGaN/GaN Schottky diode has a trend opposite to that of the GaN Schottky diode, and the dominant mechanisms are the effects of the piezoelectric polarization field and variation of two-dimensional electron gas charge density.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.60890192,60876009,and 11174182)
文摘Ni/Au Schottky contacts on A1N/GaN and A1GaN/GaN heterostructures are fabricated. Based on the measured current-voltage and capacitance-voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an A1GaN/GaN diode by self-consistently solving Schrodinger＇s and Poisson＇s equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostrncture results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an A1GaN/GaN diode.
基金the National Key R&D Program of China(2016YFA0202703)Key-Area Research and Development Program of Guangdong Province(2018B030331001)+3 种基金the National Natural Science Foundation of China(61875015,81971770,52002027,and 82071970)Beijing Natural Science Foundation(JQ20038,2214083)China National Postdoctoral Program for Innovative Talent(BX20200380)the Fundamental Research Funds for the Central Universities。
文摘Schottky-contacted sensors have been demonstrated to show high sensitivity and fast response time in various sensing systems.In order to improve their sensing performance,the Schottky barriers height(SBH)at the interface of semiconductor and metal electrode should be adjusted to appropriate range to avoid low output or low sensitivity,which was induced by excessively high or low SBH,respectively.In this work,a simple and effective SBH tuning method by triboelectric generator(TENG)is proposed,the SBH can be effectively lowered by voltage pulses generated by TENG and gradually recover over time after withdrawing the TENG.Through combining the TENG treatment with piezotronic effect,a synergistic effect on lowering SBH was achieved.The change of SBH is increased by 3.8 to 12.8 times,compared with dependent TENG treatment and piezotronic effect,respectively.Furthermore,the recovery time of the TENG-lowered SBH can be greatly shortened from 1.5 h to 40 s by piezotronic effect.This work demonstrated a flexible and feasible SBH tuning method,which can be used to effectively improve the sensitivity of Schottky-contact sensor and sensing system.Our study also shows great potential in broadening the application scenarios of Schottky-contacted electronic devices.
文摘The thermodynamic adhesion between a metal and a ceramic crystal was believed to be the result of theelectron transfer from the metal into the cerainic crystal. From an electronic point of view, such an electrontransfer at the metal/ceramic interface may be represented by the tunnelling of the metal conduction electron into the ceramic bandgap. Theoretical analysis of the quantum tunnelling process at an intimate rnetal-semicon-ductor contact were performed . and the relationship between adhesion energies and Schottky barrier heights ofvarious metal/semiconductor or insulator interfaces was dcduced .
文摘The electrical characteristics of graphene Schottky contacts formed on undoped GaN semiconductors were investigated. Excellent rectifying behavior with a rectification ratio of -10^7 at ±2 V and a low reverse leakage current of 1.0 × 10^-8 A/cm^2 at -5 V were observed. The Schottky barrier heights, as determined by the thermionic emission model Richardson plots, and barrier inhomogeneity model, were 0.90, 0.72, and 1.24 ± 0.13 eV, respectively. Despite the predicted low barrier height of -0.4 eV at the graphene-GaN interface, the formation of excellent rectifying characteristics with much larger barrier heights is attributed to the presence of a large number of surface states （1.2 x 1013 states/cm2/eV） and the internal spontaneous polarization field of GaN, resulted in a significant upward surface band bending or a bare surface barrier height as high as of 2.9 eV. Using the S parameter of 0.48 （measured from the work function dependence of Schottky barrier height） and the mean barrier height of 1.24 eV, the work function of graphene in the Au/graphene/GaN stack could be approximately estimated to be as low as 3.5 eV. The obtained results indicate that graphene is a promising candidate for use as a Schottky rectifier in GaN semiconductors with n-type conductivity.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFB0405600)the Natural Science Foundation of Tianjin City(Grant Nos.18JCYBJC85700 and18JCZDJC30500)+2 种基金the National Natural Science Foundation of China(Grant Nos.62001326,61274113,and 61404091)the Open Project of State Key Laboratory of Functional Materials for Information(Grant No.SKL202007)the Science and Technology Planning Project of Tianjin City(Grant No.20ZYQCGX00070)。
文摘Transition metal dichalcogenides(TMDCs)are promising high performance electronic materials due to their interesting semiconductor properties.However,it is acknowledged that the effective electrical contact between TMDCs-layered materials and metals remains one of the major challenges.In this work,the homogeneous monolayer MoS_(2)films with high crystalline quality were prepared by chemical vapor deposition method on SiO2/Si substrates.The back-gate field-effect transistors(FETs)were fabricated by inserting an ultrathin Al_(2)O_(3)interlayer between the metal electrodes and MoS_(2)nanosheets.With the addition of an ultrathin 0.8 nm Al_(2)O_(3)interlayer,the contact resistance decreased dramatically from 59.9 to 1.3 kΩμm and the Schottky barrier height(SBH)dropped from 102 to 27 meV compared with devices without the Al_(2)O_(3)interlayer.At the same time,the switching ratio increased from~106to~108,and both the on-current and field-effect mobility were greatly improved.We find that the ultrathin Al_(2)O_(3)interlayer can not only reduce the SBH to alleviate the Fermi level pinning phenomenon at the interface,but also protect the channel materials from the influence of air and moisture as a covering layer.In addition,the lattice and band structures of Al_(2)O_(3)/MoS_(2)film were calculated and analyzed by first-principles calculation.It is found that the total density of states of the Al_(2)O_(3)/MoS_(2)film exhibits interfacial polarized metals property,which proves the higher carrier transport characteristics.FETs with Al_(2)O_(3)interlayers have excellent stability and repeatability,which can provide effective references for future low power and high performance electronic devices.
基金supported by Youth Innovation Promotion Association CAS (2023175)the National Natural Science Foundation of China (T2125003)the Fundamental Research Funds for the Central Universities。
文摘The Schottky contact which is a crucial interface between semiconductors and metals is becoming increasingly significant in nano-semiconductor devices. A Schottky barrier, also known as the energy barrier, controls the depletion width and carrier transport across the metal–semiconductor interface.Controlling or adjusting Schottky barrier height(SBH) has always been a vital issue in the successful operation of any semiconductor device. This review provides a comprehensive overview of the static and dynamic adjustment methods of SBH, with a particular focus on the recent advancements in nanosemiconductor devices. These methods encompass the work function of the metals, interface gap states,surface modification, image-lowering effect, external electric field, light illumination, and piezotronic effect. We also discuss strategies to overcome the Fermi-level pinning effect caused by interface gap states, including van der Waals contact and 1D edge metal contact. Finally, this review concludes with future perspectives in this field.
文摘Phosphorene has attracted much attention recently as an alternative channel material in nanoscale electronic and optoelectronic devices due to its high carrier mobility and tunable direct bandgap. Compared with monolayer （ML） phosphorene, few-layer （FL） phosphorene is easier to prepare, is more stable in experiments, and is expected to form a smaller Schottky barrier height （SBH） at the phosphorene-metal interface. Using ab initio electronic structure calculations and quantum transport simulations, we perform a systematic study of the interfacial properties of three-layer （3L） phosphorene field effect transistors （FETs） contacted with several common metals （A1, Ag, Au, Cu, Ti, Cr, Ni, and Pd） for the first time. The SBHs obtained in the vertical direction from projecting the band structures of the 3L phosphorene-metal systems to the left bilayer （2L） phosphorenes are comparable with those obtained in the lateral direction from the quantum transport simulations for 2L phosphorene FETs. The quantum transport simulations for the 3L phosphorene FETs show that 3L phosphorene forms n-type Schottky contacts with electron SBHs of 0.16 and 0.28 eV in the lateral direction, when Ag and Cu are used as electrodes, respectivel~ and p-type Schottky contacts with hole SBHs of 0.05, 0.11, 0.20, 0.30, 0.30, and 0.31 eV in the lateral direction when Cr, Pd, Ni, Ti, AI, and Au are used as electrodes, respectively. The calculated polarity and SBHs of the 3L phosphorene FETs are generally in agreement with the available experiments.
文摘By means of analyzing theⅠ-Ⅴcharacteristic curve of NiSi/n-Si Schottkyjunction diodes（NiSi/n-Si SJDs）, abstracting the effective Schottky barrier height（φ_（B,eff）） and the idealfactor ofNiSi/n-Si SJDs and measuring the sheet resistance of NiSi films（R_（NiSi））,we study the effects of different dopant segregation process parameters,including impurity implantation dose,segregation annealing temperature and segregation annealing time,on theφ_（B,eff） of NiSi/ n-Si SJDs and the resistance characteristic of NiSi films.In addition,the changing rules ofφ_（B,eff） and R_（NiSi） are discussed.
