Doping of hexagonal boron nitride via intercalation: A theoretical prediction

Oba, Fumiyasu; Togo, Atsushi; Tanaka, Isao; Watanabe, Kenji; Taniguchi, Takashi

doi:10.1103/physrevb.81.075125

Cited by 67 publications

(55 citation statements)

References 55 publications

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“…Even though this is higher than the ionisation energy of shallow dopants in bulk materials such as Si or GaAs, it is lower than the dopant ionisation energies in layered BN. [28] Substitutional P is found to be a very shallow acceptor, with activation energy ∼ 0.1 eV in MoS 2 , and < 0.1 eV in WS 2 , comparable to the uncertainty of the calculation. Si is also an acceptor, though deeper.…”

supporting

confidence: 63%

Donor and acceptor levels in semiconducting transition-metal dichalcogenides

Carvalho

Neto

2014

Phys. Rev. B

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Density functional theory calculations are used to show that it is possible to dope semiconducting transition metal dichalcogenides (TMD) such as MoS2 and WS2 with electrons and/or holes either by chemical substitution or by adsorption on the sulfur layer. Notably, the activation energies of Lithium and Phosphorus, a shallow donor and a shallow acceptor, respectively, are smaller than 0.1 eV. Substitutional halogens are also proposed as alternative donors adequate for different temperature regimes. All dopants proposed result in very little lattice relaxation and, hence, are expected to lead to minor scattering of the charge carriers. Doped MoS2 and WS2 monolayers are extrinsic in a much wider temperature range than 3D semiconductors, making them superior for high temperature electronic and optoelectronic applications.Advances in the fabrication and characterization of two-dimensional (2D) dichalcogenide semiconductors have reshaped the concept of thin transistor gate. [1,2] Unlike thin fully-depleted silicon channels, physically limited by the oxide interface, single layer metal dichalcogenides are intrinsically 2D and, therefore, have no surface dangling bonds. The monolayer thickness is constant, and the scale of the variations of the electrostatic potential profile perpendicular to the plane is only limited by the extent of the electronic wavefunctions. Hence, TMD can in principle be considered immune to channel thickness modulation close to the drain.Building on these fundamental advantages, numerous field-effect transistor (FET) designs employing MoS 2 or WS 2 channels have been proposed. These range from 2D adaptations of the traditional FET structure, where the 2D semiconductor is separated by a dielectric layer from a top gate electrode, to dual-gate heterolayer devices where the transition metal dichalcogenide is straddled between two graphene sheets [2]. Such FETs can be integrated into logic inversion circuits, providing the building blocks for all logical operations [3].However, at present the success of TMD in electronics is limited by the difficulty in achieving high carrier concentrations and, by consequence, high electronic mobilities (current values range around 100 cm 2 /V.s) [4]. In the absence of a chemical doping technology, the control of the carrier concentration relies solely on the application of a gate voltage perpendicular to the layer, which shifts the Fermi level position rendering the material n-or p-type [5]. But in practice the gate voltage drop across the insulator cannot exceed its electric breakdown limit (about 1 V/nm for SiO 2 , or lower for high-κ dielectrics[6]). A work-around demonstrated in graphene consists on gating with ferroelectric polymers [7], although at the expense of the thermal stability and switching time.In this article we use first-principles calculations to show that MoS 2 and WS 2 can be doped both n-and p-type using substitutional impurities. This grants transitional metal dichalcogenides an advantage over other chalcogenide semiconductor families where ...

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supporting

confidence: 63%

Donor and acceptor levels in semiconducting transition-metal dichalcogenides

Carvalho

Neto

2014

Phys. Rev. B

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“…A hybrid HF density functional approach, which admixes the non-local Fock exchange into local or semilocal (LDA or GGA) exchange-correlation functionals, has been reported to improve the description of the electronic structure for a variety of molecules and solids [71,72,[94][95][96][97][98][99][100][101][102][103]. For ZnO, a much better reproduction of the band structure than the LDA and GGA has been demonstrated using various hybrid functionals, e.g.…”

Section: Fundamental Properties Of Znomentioning

confidence: 99%

Point defects in ZnO: an approach from first principles

Oba

Choi

Togo

et al. 2011

Science and Technology of Advanced Materials

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317

222

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Recent first-principles studies of point defects in ZnO are reviewed with a focus on native defects. Key properties of defects, such as formation energies, donor and acceptor levels, optical transition energies, migration energies and atomic and electronic structure, have been evaluated using various approaches including the local density approximation (LDA) and generalized gradient approximation (GGA) to DFT, LDA + U/GGA + U , hybrid Hartree-Fock density functionals, sX and GW approximation. Results significantly depend on the approximation to exchange correlation, the simulation models for defects and the post-processes to correct shortcomings of the approximation and models. The choice of a proper approach is, therefore, crucial for reliable theoretical predictions. First-principles studies have provided an insight into the energetics and atomic and electronic structures of native point defects and impurities and defect-induced properties of ZnO. Native defects that are relevant to the n-type conductivity and the non-stoichiometry toward the O-deficient side in reduced ZnO have been debated. It is suggested that the O vacancy is responsible for the non-stoichiometry because of its low formation energy under O-poor chemical potential conditions. However, the O vacancy is a very deep donor and cannot be a major source of carrier electrons. The Zn interstitial and anti-site are shallow donors, but these defects are unlikely to form at a high concentration in n-type ZnO under thermal equilibrium. Therefore, the n-type conductivity is attributed to other sources such as residual impurities including H impurities with several atomic configurations, a metastable shallow donor state of the O vacancy, and defect complexes involving the Zn interstitial. Among the native acceptor-type defects, the Zn vacancy is dominant. It is a deep acceptor and cannot produce a high concentration of holes. The O interstitial and anti-site are high in formation energy and/or are electrically inactive and, hence, are unlikely to play essential roles in electrical properties. Overall defect energetics suggests a preference for the native donor-type defects over acceptor-type defects in ZnO. The O vacancy, Zn interstitial and Zn anti-site have very low formation energies when the Fermi level is low. Therefore, these defects are expected to be sources of a strong hole compensation in p-type ZnO. For the n-type doping, the compensation of carrier electrons by the native acceptor-type defects can be mostly suppressed when O-poor chemical potential conditions, i.e. low O partial pressure conditions, are chosen during crystal growth and/or doping.

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“…11 A theoretical calculation indicated that the substitutional Be or Mg incorporated at a B site will act as an acceptor whereas Si or C at a B site as a donor. 12 In fact both p-and n-type conductions have been realized in cubic BN (c-BN) bulk crystals synthesized under HPHT [13][14][15] The incorporation of Si and S by in-situ doping techniques into c-BN films or films with mixed cBN/hBN phases has also been examined and the microstructures, mechanical properties as well as the field emission characteristics have been studied for these films. 16,17 To realize devices which require both p-type and n-type hBN materials, n-type conductivity control in hBN is equally important.…”

Section: Introductionmentioning

confidence: 99%

Electrical transport properties of Si-doped hexagonal boron nitride epilayers

Majety

Doan

et al. 2013

AIP Advances

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The suitability of Si as an n-type dopant in hexagonal boron nitride (hBN) wide bandgap semiconductor has been investigated. Si doped hBN epilayers were grown via in-situ Si doping by metal organic chemical vapor deposition technique. Hall effect measurements revealed that Si doped hBN epilayers exhibit n-type conduction at high temperatures (T > 800 K) with an in-plane resistivity of ∼12 Ω·cm, electron mobility of μ ∼ 48 cm2/V·s and concentration of n ∼ 1 × 1016 cm−3. Temperature dependent resistivity results yielded a Si energy level in hBN of about 1.2 eV, which is consistent with a previously calculated value for Si substitutionally incorporated into the B sites in hBN. The results therefore indicate that Si is not a suitable dopant for hBN for room temperature device applications.

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Doping of hexagonal boron nitride via intercalation: A theoretical prediction

Cited by 67 publications

References 55 publications

Donor and acceptor levels in semiconducting transition-metal dichalcogenides

Donor and acceptor levels in semiconducting transition-metal dichalcogenides

Point defects in ZnO: an approach from first principles

Electrical transport properties of Si-doped hexagonal boron nitride epilayers

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