Theoretical study on the possibility of bipolar doping of ScN

Influences of ALD Al$_2$O$_3$ on the surface band-bending of c-plane, Ga-face GaN and the implication to GaN-collector npn heterojunction bipolar transistors

Due to the lack of effective p-type doping in GaN and the adverse effects of surface band-bending of GaN on electron transport, developing practical GaN heterojunction bipolar transistors has been impossible. The recently demonstrated approach of grafting n-type GaN with p-type semiconductors, like Si and GaAs, by employing ultrathin (UO) Al$_2$O$_3$ at the interface of Si/GaN and GaAs/GaN, has shown the feasibility to overcome the poor p-type doping challenge of GaN by providing epitaxy-like interface quality. However, the surface band-bending of GaN that could be influenced by the UO Al2O3 h…

Electronic Excitations and Insulator-Metal Transition in Poly(3-hexylthiophene) Organic Field-Effect Transistors

We carry out a comprehensive theoretical and experimental study of charge injection in Poly(3-hexylthiophene) (P3HT) to determine the most likely scenario for metal-insulator transition in this system. We calculate the optical absorption frequencies corresponding to a polaron and a bipolaron lattice in P3HT. We also analyze the electronic excitations for three possible scenarios under which a first-- or a second--order metal--insulator transition can occur in doped P3HT. These theoretical scenarios are compared with data from infrared absorption spectroscopy on P3HT thin film field-effect tran…

Boron phosphide films by reactive sputtering: Searching for a p-type transparent conductor

With an indirect band gap in the visible and a direct band gap at a much higher energy, boron phosphide (BP) holds promise as an unconventional p-type transparent conductor. Previous experimental reports deal almost exclusively with epitaxial, nominally undoped BP films by chemical vapor deposition. High hole concentrations were often observed, but it is unclear if native defects alone can be responsible for it. Besides, the feasibility of alternative deposition techniques has not been clarified and optical characterization is generally lacking. In this work, we demonstrate reactive sputtering…

Metal$/BaTiO_{3}/β-Ga_{2}O_{3}$ Dielectric Heterojunction Diode with 5.7 MV/cm Breakdown Field

Wide and ultra-wide band gap semiconductors can provide excellent performance due to their high energy band gap, which leads to breakdown electric fields that are more than an order of magnitude higher than conventional silicon electronics. In materials where p-type doping is not available, achieving this high breakdown field in a vertical diode or transistor is very challenging. We propose and demonstrate the use of dielectric heterojunctions that use extreme permittivity materials to achieve high breakdown field in a unipolar device. We demonstrate the integration of a high permittivity mate…

SnTe中Zn杂质的双重特性：调控热电与拓扑性质

On the dual character of Zn impurity in SnTe: Tuning thermoelectric and topological properties

该研究通过第一性原理计算揭示Zn掺杂SnTe中Zn的双重作用：在导带形成类共振态增强n型热电性能，在价带诱导带收敛提升p型性能，并驱动拓扑相变，实现热电与拓扑性质的协同调控。

NbOCl₂单层中平带的起源与特性

Origin and properties of the flat band in NbOCl2 monolayer

本研究结合密度泛函理论与多体量子微扰理论，探究了NbOCl₂单层平带的起源及多种物性，发现其平带来自佩尔斯畸变与Nb电子构型的相互作用，且该材料在电子、光电子及自旋电子学领域具有应用潜力。

金属与p型GaN接触的基础原理：新型多层设计

Fundamentals of the metal contact to p-type GaN: new multilayer design

通过ab initio和漂移-扩散计算模拟p型GaN接触电学特性，提出采用深能级受主多层注入的新型接触设计，有望降低电阻并消除高效氮化物光电器件中的能量损失与过度发热障碍。

Correlation between corrugation-induced flexoelectric polarization and conductivity of low-dimensional transition metal dichalcogenides

Tunability of polar and semiconducting properties of low-dimensional transition metal dichalcogenides (TMDs) have propelled them to the forefront of fundamental and applied physical research. These materials can vary from non-polar to ferroelectric, and from direct-band semiconductor to metallic. However, in addition to classical controls such as composition, doping, and field effect in TMDs the additional degrees of freedom emerge due to the curvature-induced electron redistribution and associated changes in electronic properties. Here we numerically explore the elastic and electric fields, f…