Inelastic phonon transport across atomically sharp metal/semiconductor interfaces

Understanding thermal transport across metal/semiconductor interfaces is crucial for heat dissipation of electronics The dominant heat carriers in non-metals, phonons, transport elastically across most interfaces, except for a few extreme cases where the two materials that formed the interface are highly dissimilar with a large difference in Debye temperature. In this work we show that even for two materials with similar Debye temperatures (Al/Si, Al/GaN), a substantial portion of phonons will transport inelastically across their interfaces at high temperatures, significantly enhancing interface thermal conductance. Moreover, we find that interface roughness strongly affects phonon transport process. For atomically sharp interfaces, phonons are allowed to transport inelastically and interface thermal conductance linearly increases at high temperatures. With increasing interface roughness, inelastic phonon transport rapidly diminishes. Our results provide new insights on phonon transport across interfaces and open up opportunities to engineering interface thermal conductance specifically for materials of relevance to microelectronics.

Numerical Design of Carrier Transporting Layer in Top-Gate InGaZnO Thin-Film Transistors for Controlling Potential Energy

Top-gate amorphous indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) are designed with numerical analysis to control their electron potential energy. Design simulations show the effects of structural design on the electrical characteristics of these TFTs. In particular, the thicknesses of the channel (tch) and conducting (tc) layers, which play vital roles in TFT electrical performance, are varied from 1 to 50 nm to investigate the effect of thicknesses on the electron potential energies of the channel region and the electrode-semiconductor interfaces. The potential energies are precisely optimized for efficient charge transport, injection, and extraction, thus enhancing the electrical performance of these devices. It is also demonstrated that tch mainly affects mobility and threshold voltage, while tc mainly affects on-current. An acceptable threshold voltage of 0.55 V and high mobility of 14.7 cm2V−1s−1 are obtained with a tch of 30 nm and tc of 10 nm. Controllability of the electron potential energies and electrical performance of IGZO TFTs by means of structural design will contribute to realization of next-generation displays that have large areas and high resolutions.

A Review of Recent Developments in Molecular Dynamics Simulations of the Photoelectrochemical Water Splitting Process

In this review, we provide a short overview of the Molecular Dynamics (MD) method and how it can be used to model the water splitting process in photoelectrochemical hydrogen production. We cover classical non-reactive and reactive MD techniques as well as multiscale extensions combining classical MD with quantum chemical and continuum methods. Selected examples of MD investigations of various aqueous semiconductor interfaces with a special focus on TiO2 are discussed. Finally, we identify gaps in the current state-of-the-art where further developments will be needed for better utilization of MD techniques in the field of water splitting.

Computing with DFT Band Offsets at Semiconductor Interfaces: A Comparison of Two Methods

Two DFT-based methods using hybrid functionals and plane-averaged profiles of the Hartree potential (individual slabs versus vacuum and alternating slabs of both materials), which are frequently used to predict or estimate the offset between bands at interfaces between two semiconductors, are analyzed in the present work. These methods are compared using several very different semiconductor pairs, and the conclusions about the advantages of each method are discussed. Overall, the alternating slabs method is recommended in those cases where epitaxial mismatch does not represent a significant problem.