One of the fundamental properties of semiconductors is their ability to support highly tunable electric currents in the presence of electric fields or carrier concentration gradients. These properties are described by transport coefficients such as electron and hole mobilities. Over the last decades, our understanding of carrier mobilities has largely been shaped by experimental investigations and empirical models. Recently, advances in electronic structure methods for real materials have made it possible to study these properties with predictive accuracy and without resorting to empirical parameters. These new developments are unlocking exciting new opportunities, from exploring carrier transport in quantum matter to in silico designing new semiconductors with tailored transport properties. In this article, we review the most recent developments in the area of ab initio calculations of carrier mobilities of semiconductors. Our aim is threefold: to make this rapidly-growing research area accessible to a broad community of condensed-matter theorists and materials scientists; to identify key challenges that need to be addressed in order to increase the predictive power of these methods; and to identify new opportunities for increasing the impact of these computational methods on the science and technology of advanced materials. The review is organized in three parts. In the first part, we offer a brief historical overview of approaches to the calculation of carrier mobilities, and we establish the conceptual framework underlying modern ab initio approaches. We summarize the Boltzmann theory of carrier transport and we discuss its scope of applicability, merits, and limitations in the broader context of many-body Green's function approaches. We discuss recent implementations of the Boltzmann formalism within the context of density functional theory and many-body perturbation theory calculations, placing an emphasis on the key computational challenges and suggested solutions. In the second part of the article, we review applications of these methods to materials of current interest, from three-dimensional semiconductors to layered and two-dimensional materials. In particular, we discuss in detail recent investigations of classic materials such as silicon, diamond, gallium arsenide, gallium nitride, gallium oxide, and lead halide perovskites as well as low-dimensional semiconductors such as graphene, silicene, phosphorene, molybdenum disulfide, and indium selenide. We also review recent efforts toward high-throughput calculations of carrier transport. In the last part, we identify important classes of materials for which an ab initio study of carrier mobilities is warranted. We discuss the extension of the methodology to study topological quantum matter and materials for spintronics and we comment on the possibility of incorporating Berry-phase effects and many-body correlations beyond the standard Boltzmann formalism.

https://iopscience.iop.org/article/10.1088/1361-6633/ab6a43/pdf

First-principles calculations of charge carrier mobility and conductivity in bulk semiconductors and two-dimensional materials

Two-dimensional crystals have emerged as a class of materials that may impact future electronic technologies. Experimentally identifying and characterizing new functional two-dimensional materials is challenging, but also potentially rewarding. Here, we fabricate field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometres. Reliable transistor performance is achieved at room temperature in samples thinner than 7.5 nm, with drain current modulation on the order of 10(5) and well-developed current saturation in the I-V characteristics. The charge-carrier mobility is found to be thickness-dependent, with the highest values up to ∼ 1,000 cm(2) V(-1) s(-1) obtained for a thickness of ∼ 10 nm. Our results demonstrate the potential of black phosphorus thin crystals as a new two-dimensional material for applications in nanoelectronic devices.

http://absimage.aps.org/image/MAR14/MWS_MAR14-2013-005031.pdf

Black Phosphorus Field-effect Transistors

Graphene-like carbon-nitrogen materials as anode materials for Li-ion and mg-ion batteries

2D GeP as a Novel Broadband Nonlinear Optical Material for Ultrafast Photonics

Two-dimensional (2D) crystalline carbon nitrides (CxNy) with graphene-like atomic structures but semiconducting nature are new appealing materials, and increasing interest has been focused on their synthesis, properties, and applications. Apart from the well-known graphitic carbon nitride (g-C3N4), other types of 2D CxNy nanocrystals including C2N, C3N and C5N2 are also successfully fabricated in recent years and their properties and potential uses in various fields have been widely investigated. Meanwhile, g-CN, C2N2, C2N3 and C5N have been theoretically predicted, and their properties and potential applications have also been researched. Until now, 2D crystalline CxNy compounds have demonstrated promising applications in photocatalysis, electrocatalysis, gas adsorption/separation, and energy storage devices, from both experimental and theoretical aspects, stemming from their unique geometric structures, tunable electronic properties, and high specific surface area. Herein, recent advances in the synthesis of 2D CxNy nanocrystals and their applications in various fields are summarized. Moreover, future challenges and opportunities for developing 2D CxNy nanocrystals for more broad applications including environmental remediation are also discussed.

Novel two-dimensional crystalline carbon nitrides beyond g-C3N4: structure and applications

Recently, two-dimensional (2D) GeP semiconductor was successfully obtained from single crystals using mechanical exfoliation method. In this study, uniaxial strain behaviors and carrier mobilities of monolayer GeP are investigated by first principles calculations. The stretching simulation shows that monolayer GeP can maintain a stable elastic deformation for x axis strain from zero to ɛ = 12.9%, and y axis strain from zero to ɛ  = 26.2%. The structural stability can be further verified by the phonon dispersion. Carrier mobility based on acoustic deformation potential scattering mechanism is predicted by the calculations of effective mass, elastic modulus and deformation potential. The upper limits of some possible carrier mobilities are presented, and they can be tuned by uniaxial strain. Combining excellent mechanical properties with moderate band gap and tunable carrier mobility, 2D GeP has a potential application in nanoelectronics and optoelectronics.

Strain behavior and Carrier mobility for novel two-dimensional semiconductor of GeP: First principles calculations

Traditional metal-oxide semiconductor devices are inadequate for use in artificial neural networks (ANNs) owing to their high power consumption, complex structures, and difficult fabrication techniques. Resistive random access memory (RRAM) is a promising candidate for ANNs owing to its simple structure, low power consumption, and excellent compatibility with CMOS. Moreover, it can mimic synaptic functions because of its multilevel resistive switching (RS) behavior. Herein, we demonstrate highly uniform RS and a high on/off ratio of RRAM based on graphene oxide by embedding gold nanoparticles into the device. This allowed reliable multilevel storage. Further, multilevel RRAM based on spike-timing-dependent-plasticity learning rules was used for image pattern recognition. These findings may offer a route to develop reliable digital memristors for ANNs.

Uniform multilevel switching of graphene oxide-based RRAM achieved by embedding with gold nanoparticles for image pattern recognition

First principles calculations are performed to predict phonon-limited carrier mobility for a novel graphene-like semiconductor with BC6N stoichiometry. First, the electron–phonon interaction matrix element (EPIME) from the standard Wannier and polar Wannier interpolation schemes is used to investigate mobility. After considering the polarization, carrier mobility is greatly reduced, so polar optical phonon (POP) scattering plays an important role. At 300 K, the electron mobility for the most stable BC6N–B is predicted to be μx = 4.51 × 102–8.37 × 102 and μy = 8.35 × 102–1.22 × 103 cm2 V−1 s−1, while the hole mobility is estimated to be μx = 4.79 × 102–8.65 × 102 and μy = 9.19 × 102–1.28 × 103 cm2 V−1 s−1. Then, the longitudinal acoustic phonon deformation potential theory (LAP-DPT) is adopted to calculate the mobility, which leads to an overestimation for carrier mobility in polar semiconductors. Furthermore, the semiempirical model based on the POP scattering is also used to investigate the mobility. It is confirmed that the intrinsic mobility for BC6N is mainly determined by the Frohlich interaction. The investigation provides a deep understanding of carrier transport properties. It is revealed that B and N co-doped graphene may become a promising material for application in nanoelectronic devices due to the excellent mechanical behavior, moderate direct band gap and high carrier mobility.

Prediction of high carrier mobility for a novel two-dimensional semiconductor of BC6N: first principles calculations

Elastic behavior and intrinsic carrier mobility for monolayer SnS and SnSe: First-principles calculations

Recently, a novel two-dimensional (2D) semiconductor, InSe, has attracted great attention due to its potential applications in optoelectronic devices and field effect transistors. In this study, phonon-limited mobility is investigated by the first-principles calculation. At 300 K, the intrinsic electron mobilities calculated from the electron-phonon coupling (EPC) matrix element are as high as [Formula: see text] (zigzag direction) and [Formula: see text] [Formula: see text] (Armchair direction), respectively. The deformation potential theory (DPT) based on longitudinal acoustic and optical phonon scattering is also employed to investigate electron mobility. The mobility from optical phonon scattering is much higher than that from longitudinal acoustic phonon scattering. If the polarization characteristics of InSe are not considered, the electron mobility calculated from EPC matrix element is closed to that from the longitudinal acoustic phonon DPT. In this study, we have also investigated the effect of polarization properties in 2D InSe on electron mobility. At 300 K, the electron mobility for including Frohlich interaction is reduced to [Formula: see text] and [Formula: see text] [Formula: see text]. Therefore, the electron mobility for InSe is controlled by the scattering from polar phonons. The mobility can be increased to [Formula: see text] and [Formula: see text] [Formula: see text] under 4% biaxial strain. This result is compared with the experiment, and some disagreements are explained.

https://iopscience.iop.org/article/10.1088/1361-648X/ab534f/pdf

Shuo Cao

Papers

Strain behavior and Carrier mobility for novel two-dimensional semiconductor of GeP: First principles calculations

Uniform multilevel switching of graphene oxide-based RRAM achieved by embedding with gold nanoparticles for image pattern recognition

Prediction of high carrier mobility for a novel two-dimensional semiconductor of BC6N: first principles calculations

Elastic behavior and intrinsic carrier mobility for monolayer SnS and SnSe: First-principles calculations

Theoretical prediction of intrinsic electron mobility of monolayer InSe: first-principles calculation.