Two-dimensional semiconductors have attracted immense research interests owing to their intriguing properties and promising applications in electronic and optoelectronic devices.However,the performance of these device...Two-dimensional semiconductors have attracted immense research interests owing to their intriguing properties and promising applications in electronic and optoelectronic devices.However,the performance of these devices is drastically hindered by the large Schottky barrier at the electric contact interface,which is hardly tunable due to the Fermi level pinning effect.In this review,we will analyze the root causes of the contact problems for the two-dimensional semiconductor devices and summarize the strategies on the basis of different contact geometries,aiming to lift out the Fermi level pinning effect and achieve the ohmic contact.Moreover,the remarkable improvement of the device performance thanks to these optimized contacts will be emphasized.At the end,the merits and limitations of these strategies will be discussed as well,which potentially gives a guideline for handling the electric contact issues in two-dimensional semiconductors devices.展开更多
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
The dependences of Fermi-level pinning on interface state densities for the metal-dielectric, ploycrystalline silicon-dielectric, and metal silicide-dielectric interfaces are investigated by calculating their effectiv...The dependences of Fermi-level pinning on interface state densities for the metal-dielectric, ploycrystalline silicon-dielectric, and metal silicide-dielectric interfaces are investigated by calculating their effective work functions and their pinning factors. The Fermi-level pinning factors and effective work functions of the metal-dielectric interface are observed to be more susceptible to the increasing interface state densities, differing significantly from that of the ploycrystalline silicon-dielectric interface and the metal silicide-dielectric interface. The calculation results indicate that metal silicide gates with high-temperature resistance and low resistivity are a more promising choice for the design of gate materials in metal-oxide semiconductor（MOS） technology.展开更多
Insertion of a C-containing layer in a metal/Ge structure,using a chemical bath,enabled the Schottky barrier height（SBH） to be modulated.Chemical baths with 1-octadecene,1-hexadecene,1-tetradecene,and 1- dodecene we...Insertion of a C-containing layer in a metal/Ge structure,using a chemical bath,enabled the Schottky barrier height（SBH） to be modulated.Chemical baths with 1-octadecene,1-hexadecene,1-tetradecene,and 1- dodecene were used separately with Ge substrates.An ultrathin C-containing layer stops the penetration of free electron wave functions from the metal to the Ge.Metal-induced gap states are alleviated and the pinned Fermi level is released.The SBH is lowered to 0.17 eV.This new formation method is much less complex than traditional ones,and the result is very good.展开更多
基金supported by the National Natural Science Foundation of China(21825103,51727809)the National Basic Research Program of China(2015CB932600)the Fundamental Research Funds for the Central University(2019kfy XMBZ018)
文摘Two-dimensional semiconductors have attracted immense research interests owing to their intriguing properties and promising applications in electronic and optoelectronic devices.However,the performance of these devices is drastically hindered by the large Schottky barrier at the electric contact interface,which is hardly tunable due to the Fermi level pinning effect.In this review,we will analyze the root causes of the contact problems for the two-dimensional semiconductor devices and summarize the strategies on the basis of different contact geometries,aiming to lift out the Fermi level pinning effect and achieve the ohmic contact.Moreover,the remarkable improvement of the device performance thanks to these optimized contacts will be emphasized.At the end,the merits and limitations of these strategies will be discussed as well,which potentially gives a guideline for handling the electric contact issues in two-dimensional semiconductors devices.
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.61376096,61327813,and 11234007)
文摘The dependences of Fermi-level pinning on interface state densities for the metal-dielectric, ploycrystalline silicon-dielectric, and metal silicide-dielectric interfaces are investigated by calculating their effective work functions and their pinning factors. The Fermi-level pinning factors and effective work functions of the metal-dielectric interface are observed to be more susceptible to the increasing interface state densities, differing significantly from that of the ploycrystalline silicon-dielectric interface and the metal silicide-dielectric interface. The calculation results indicate that metal silicide gates with high-temperature resistance and low resistivity are a more promising choice for the design of gate materials in metal-oxide semiconductor（MOS） technology.
基金financially supported by the National Natural Science Foundation of China(62074130)the Natural Science Basic Research Plan in Shaanxi Province of China(2021JM-057)+1 种基金the Research Fund of the State Key Laboratory of Solidification Processing(Northwestern Polytechnical University(NPU),2021-TS-09)the Testing Fund Project of Analysis and Testing Center(NPU)(2021T017)。
基金supported by the Chinese National Key Basic Research Program(No.2011CBA00602)the National Key Scientific and Technological Projects,China(Nos.2009ZX02035-004-02,2011ZX02708-002)
文摘Insertion of a C-containing layer in a metal/Ge structure,using a chemical bath,enabled the Schottky barrier height（SBH） to be modulated.Chemical baths with 1-octadecene,1-hexadecene,1-tetradecene,and 1- dodecene were used separately with Ge substrates.An ultrathin C-containing layer stops the penetration of free electron wave functions from the metal to the Ge.Metal-induced gap states are alleviated and the pinned Fermi level is released.The SBH is lowered to 0.17 eV.This new formation method is much less complex than traditional ones,and the result is very good.
