Two-Dimensional Dielectrics for Future Electronics: Hexagonal Boron Nitride, Oxyhalides, Transition-Metal Nitride Halides, and Beyond

Abstract

Recent developments in the field of two-dimensional (2D) van der Waals (vdW) dielectrics have captured great interest because of potential applications of 2D materials in future generations of complementary metal-oxide semiconductor (CMOS) technologies. In this Spotlight article, we highlight the progress we recently made toward the discovery of 2D vdW dielectrics, which will be critical to realizing a vdW transistor technology. We provide an overview of how to calculate the dielectric properties of 2D vdW dielectric candidates from first-principles using density functional theory. Furthermore, we show how to quantify the anticipated leakage current through a 2D vdW dielectric. We illustrate the use of hexagonal boron nitride (h-BN), oxyhalides, transition-metal nitride halides (TMNH), and alkaline hydroxides.

Toward Sustainable Ultrawide Bandgap van der Waals Materials: An ab initio Screening Effort

“…Here, we assess if any of the sub‐nm EOT candidates can outperform hBN under the same set‐up, which requires a leakage currents below 0.01 A cm −2 for gate voltages | V G | ⩽ 0.7 V. [ 75 ] We estimate the leakage currents based on the Tsu–Esaki formalism [ 80 ] implemented in Comphy, [ 81,82 ] though we note that other tunneling equations, such as the Fowler–Nordheim [ 83 ] and Richardson–Dushmann [ 84,85 ] laws, can also be used for the modelling of gate leakage current. [ 36,63,76,77 ]…”

“…[73] Although few-layer hBN is regarded as a promising ultrathin vdW gate dielectric for transistor miniaturization, sub-nm equivalent oxide thickness (EOT) hBN exhibits unacceptably high leakage currents. [72,74,75] The search for performant layered dielectrics [36,63,76,77] is, however, a challenging quest due to the simultaneous requirements of high 𝜅, low interfacial defects, high breakdown strength [78] and an appropriate band alignment with the channel semiconductor. [79] Based on the EOT and leakage current requirements, prospective gate dielectrics are identified from the UWBG candidates as follows.…”

“…Here, we assess if any of the sub-nm EOT candidates can outperform hBN under the same set-up, which requires a leakage currents below 0.01 A cm −2 for gate voltages |V G | ⩽ 0.7 V. [75] We estimate the leakage currents based on the Tsu-Esaki formalism [80] implemented in Comphy, [81,82] though we note that other tunneling equations, such as the Fowler-Nordheim [83] and Richardson-Dushmann [84,85] laws, can also be used for the modelling of gate leakage current. [36,63,76,77] In the Tsu-Esaki model, the tunneling effective mass m diel tun is commonly extracted from experimental data in bulk dielectrics based on specific charge transport models. [86] For ultrathin vdW materials, however, more care is required in estimating vertical tunneling masses since the vertical effective mass of the layered bulk arises due to the out-of-plane crystal periodicity, a feature that is completely absent in few-layer vdW materials.…”

(Invited) Bulk Traps in Layered 2D Gate Dielectrics

“…Recent theoretical calculations of other 2D insulating materials identified a number of potential dielectrics (5,6). Of these, a class of nitride chlorides, oxychlorides, and hydroxide compounds were identified with a range of properties.…”

Size and strain modulation of dielectric constant on atomic bond relaxation

“…Theoretically, the size-induced dielectric constant reduction is presently explained from the perspective of quantum confinement [12], bond theory [22], and thermodynamics [11]. Numerous calculation methods have been developed to analyze the size-dependent dielectric constant of TMDs, including the density functional theory [4,[23][24][25][26][27], full potential linearized augmented plane wave method [7,28], ab initio calculations [8,29], and quasiparticle self-consistent calculations [30]. For the mechanical strain-induced dielectric constant rising in TMDs system, it is presently investigated by mainly using density functional theory [31][32][33][34][35][36].…”