| AVS 61st International Symposium & Exhibition | |
| Accelerating Materials Discovery for Global Competitiveness Focus Topic | Wednesday Sessions |
| Session MG-WeM |
| Session: | Design of New Materials |
| Presenter: | Douglas Irving, North Carolina State University |
| Authors: | B.E. Gaddy, North Carolina State University Z.A. Bryan, North Carolina State University I.S. Bryan, North Carolina State University R. Kirste, North Carolina State University J. Xie, Hexatech Inc. R. Dalmau, Hexatech Inc. B. Moody, Hexatech Inc. Y. Kumagai, Tokyo University of Agriculture and Technology, Japan T. Nagashima, Tokuyama Corporation, Japan Y. Kubota, Tokuyama Corporation, Japan T. Kinoshita, Tokuyama Corporation, Japan A. Koukitu, Tokyo University of Agriculture and Technology, Japan R. Collazo, North Carolina State University Z. Sitar, North Carolina State University D.L. Irving, North Carolina State University |
| Correspondent: | Click to Email |
Semiconductors obtain new functionality by the incorporation of dilute concentrations of impurities. This principle has been utilized to tailor the properties of narrow gap semiconductors, such as Si or GaAs, but tailoring the properties of wide band gap materials for optical or high power applications has been extremely challenging. As a result, there has been slow progress in identifying new material combinations (bulk material + dilute dopants) to enable novel functionality. To help overcome these obstacles, we have developed and implemented a point defects database in which we store formation, ionization, and optical transition energies determined by hybrid exchange-correlation density functional theory methods. These predictions from first principles are then strongly coupled with synthesis and characterization efforts to identify troublesome point defects and also suggest routes to realizing desired properties if particular defect cannot be removed. The stored data is also used to solve mass balance equations to determine the number of carriers and compensating defects. In this talk, I will present our recent efforts in applying these tools to determine solutions for unwanted optical absorption in AlN grown by PVT. With our data we have demonstrated that substitutional carbon on the nitrogen site is a deep acceptor. When ionized it is the source of unwanted optical absorption. This was confirmed by PL, SIMS, and HVPE. Solution of mass balance equations reveals that the compensating defect is a singly ionized nitrogen vacancy for relevant growth conditions. The presence of this defect has been confirmed by an optical emission predicted to originate from a donor acceptor pair recombination and measured by PLE spectroscopy. When carbon cannot be removed from the growth process, we have used our database to determine mechanisms important to removing unwanted optical absorption in high carbon samples. In total, this approach has accelerated the design of new materials and also led to deeper understanding of the important mechanisms, which will impact future efforts to tailor properties of AlN and its alloys.