@article{mullen_boulton_pan_kim_2024, title={Electronic properties of c-BN/diamond heterostructures for high-frequency high-power applications}, volume={143}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2024.110920}, abstractNote={Using first principles calculations, this work investigates the suitability of diamond/c-BN heterojunctions for high frequency, high power device applications. The key quantities of band offsets and interface charge polarization are examined for different crystallographic orientations [(110), (111), or (100)], bond terminations (CB or CN), and substrates (diamond or c-BN). The results indicate that both the (111) and (100) structures with polar interfaces are likely to be a type-I alignment with the diamond conduction and valence band extrema nested within the c-BN bandgap, whereas the non-polar (110) counterpart may form type II as the valence band of c-BN is shifted down substantially lower. The valence band offsets are estimated to be around 0.2–0.55 eV and 1.2–1.3 eV for types I and II, respectively, with only a modest dependence on the order of layer stacking and bond termination. The (111) and (100) structures also show net charge polarization in a narrow region at the interface. The electron-deficient and electron-rich nature of the CB and CN bonding are found to induce charge redistribution leading to an essentially 2D sheet of negative and positive polarization, respectively, with a density on the order of 1012−1013q/cm2 (q=1.6×10−19 C). With the predicted band alignments suitable for carrier confinement as well as the possibility of the modulation and polarization doping, the diamond/c-BN heterostructures are a promising candidate for high-performance electronic devices with a highly conductive 2D channel. Both p-type and n-type devices appear possible with a judicious choice of the heterojunction configuration.}, journal={DIAMOND AND RELATED MATERIALS}, author={Mullen, Jeffrey T. and Boulton, James A. and Pan, Minghao and Kim, Ki Wook}, year={2024}, month={Mar} }
 @article{pan_mullen_kim_2021, title={First-principles analysis of magnetically doped transition-metal dichalcogenides}, volume={54}, ISSN={["1361-6463"]}, DOI={10.1088/1361-6463/abbb48}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF PHYSICS D-APPLIED PHYSICS}, author={Pan, Minghao and Mullen, Jeffrey T. and Kim, Ki Wook}, year={2021}, month={Jan} }
 @article{jin_mullen_kim_2016, title={Highly anisotropic electronic transport properties of monolayer and bilayer phosphorene from first principles}, volume={109}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4960526}, DOI={10.1063/1.4960526}, abstractNote={The intrinsic carrier transport dynamics in phosphorene is theoretically examined. Utilizing a density functional theory treatment, the low-field mobility and the saturation velocity are characterized for both electrons and holes in the monolayer and bilayer structures. The analysis clearly elucidates the crystal orientation dependence manifested through the anisotropic band structure and the carrier-phonon scattering rates. In the monolayer, the hole mobility in the armchair direction is estimated to be approximately five times larger than in the zigzag direction at room temperature (460 cm2/V s vs. 90 cm2/V s). The bilayer transport, on the other hand, exhibits a more modest anisotropy with substantially higher mobilities (1610 cm2/V s and 760 cm2/V s, respectively). The calculations on the conduction-band electrons indicate a comparable dependence while the characteristic values are generally smaller by about a factor of two. The variation in the saturation velocity is found to be less pronounced. With the anticipated superior performance and the diminished anisotropy, few-layer phosphorene offers a promising opportunity particularly in p-type applications.}, number={5}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Jin, Zhenghe and Mullen, Jeffrey T. and Kim, Ki Wook}, year={2016}, month={Aug}, pages={053108} }
 @article{jin_li_mullen_kim_2014, title={Intrinsic transport properties of electrons and holes in monolayer transition-metal dichalcogenides}, volume={90}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.90.045422}, DOI={10.1103/physrevb.90.045422}, abstractNote={Intrinsic electron- and hole-phonon interactions are investigated in monolayer transition-metal dichalcogenides $M{X}_{2}$ (M=Mo, W; X=S, Se) based on a density functional theory formalism. Due to their structural similarities, all four materials exhibit qualitatively comparable scattering characteristics with the acoustic phonons playing a dominant role near the conduction and valence band extrema at the K point. However, substantial differences are observed quantitatively leading to disparate results in the transport properties. Of those considered, ${\mathrm{WS}}_{2}$ provides the best performance for both electrons and holes with high mobilities and saturation velocities in the full-band Monte Carlo analysis of the Boltzmann transport equation. It is also found that monolayer $M{X}_{2}$ crystals with an exception of ${\mathrm{MoSe}}_{2}$ generally show hole mobilities comparable to or even larger than the value for bulk silicon at room temperature, suggesting a potential opportunity in p-type devices. The analysis is extended to estimate the effective deformation potential constants for a simplified treatment as well.}, number={4}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Jin, Zhenghe and Li, Xiaodong and Mullen, Jeffrey T. and Kim, Ki Wook}, year={2014}, month={Jul} }