Miso Lee

Property database for single-element doping in ZnO obtained by automated first-principles calculations.

Throughout the past decades, doped-ZnO has been widely used in various optical, electrical, magnetic, and energy devices. While almost every element in the Periodic Table was doped in ZnO, the systematic computational study is still limited to a small number of dopants, which may hinder a firm understanding of experimental observations. In this report, we systematically calculate the single-element doping property of ZnO using first-principles calculations. We develop an automation code that enables efficient and reliable high-throughput calculations on thousands of possible dopant configurations. As a result, we obtain formation-energy diagrams for total 61 dopants, ranging from Li to Bi. Furthermore, we evaluate each dopant in terms of n-type/p-type behaviors by identifying the major dopant configurations and calculating carrier concentrations at a specific dopant density. The existence of localized magnetic moment is also examined for spintronic applications. The property database obtained here for doped ZnO will serve as a useful reference in engineering the material property of ZnO through doping.

Computational discovery of p-type transparent oxide semiconductors using hydrogen descriptor

The ultimate transparent electronic devices require complementary and symmetrical pairs of n-type and p-type transparent semiconductors. While several n-type transparent oxide semiconductors like InGaZnO and ZnO are available and being used in consumer electronics, there are practically no p-type oxides that are comparable to the n-type counterpart in spite of tremendous efforts to discover them. Recently, high-throughput screening with the density functional theory calculations attempted to identify candidate p-type transparent oxides, but none of suggested materials was verified experimentally, implying need for a better theoretical predictor. Here, we propose a highly reliable and computationally efficient descriptor for p-type dopability—the hydrogen impurity energy. We show that the hydrogen descriptor can distinguish well-known p-type and n-type oxides. Using the hydrogen descriptor, we screen most binary oxides and a selected pool of ternary compounds that covers Sn2+-bearing and Cu1+-bearing oxides as well as oxychalcogenides. As a result, we suggest La2O2Te and CuLiO as promising p-type oxides.Transparent oxides: p-type huntingComputational studies screen transparent oxide semiconductors based on the formation energy of a particular defect, and reveal promising hole-doped candidates. Although p-doped semiconductors are useful for electronic devices, their performance so far is not comparable to their n-type counterparts: most p-type oxides have stability issues or suffer from poor transparency. Now a team from Seoul National University and the Electronics and Telecommunications Research Institute in Daejeon, South Korea, are computationally looking for p-doped oxides with high conductivity and good transparency, simultaneously. Their screening relies on defect chemistry and assesses the dopability of the materials by using the formation energy of hydrogen interstitial defect, as well as the evaluation of the hole mass. Authors put forth a few promising p-type binary oxides and ternary compounds, which can be very useful for implementing electronic devices, once their properties have been verified experimentally.

High-throughput ab initio calculations on dielectric constant and band gap of non-oxide dielectrics

High-k dielectrics, materials having a large band gap (Eg) and high dielectric constant (k) simultaneously, constitute critical components in microelectronic devices. Because of the inverse relationship between Eg and k, materials with large values in both properties are rare. Therefore, massive databases on Eg and k will be useful in identifying optimal high-k materials. While experimental and theoretical data on Eg and k of oxides are accumulating, corresponding information is scarce for non-oxide dielectrics with anions such as C, N, F, P, S, and Cl. To identify promising high-k dielectrics among these material groups, we screen 869 compounds of binary carbides, nitrides, sulfides, phosphides, chlorides, and fluorides, through automated ab initio calculations. Among these compounds, fluorides exhibit an Eg-k relation that is comparable to that of oxides. By further screening over ternary fluorides, we identify fluorides such as BiF3, LaF3, and BaBeF4 that could serve as useful high-k dielectrics.