AVS 64th International Symposium & Exhibition
    Electronic Materials and Photonics Division Wednesday Sessions
       Session EM-WeM

Invited Paper EM-WeM1
Electrons and Phonons in Amorphous Semiconductors

Wednesday, November 1, 2017, 8:00 am, Room 14

Session: Charge Transport in Disordered Materials
Presenter: David Drabold, Ohio University
Authors: D. Drabold, Ohio University
K. Prasai, Ohio University
P. Biswas, University of Southern MIssissippi
Correspondent: Click to Email
The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this talk, we explore the electron-lattice coupling using current tools of first-principles computer simulation. We choose three materials to illustrate the phenomena: amorphous silicon, amorphous selenium, and amorphous gallium nitride. In each case, we show that there is a strong correlation between the localization of electron states and the magnitude of thermally-induced fluctuations in energy eigenvalues obtained from density-functional theory (i.e. Kohn-Sham eigenvalues). We provide a heuristic theory to explain these observations. The case of amorphous GaN, a topologically disordered partly ionic insulator, is distinctive compared to the covalent amorphous systems. We close by showing how the optical gap of an amorphous semiconductor can be computationally engineered with the judicious use of Hellmann-Feynman forces (associated with a few defect states) using molecular dynamics simulations. These forces can be used to close or open an optical gap, and identify a structure with a prescribed gap. We use the approach with plane-wave density functional methods to identify the conducting state of a conducting bridge memory material: Ag-doped GeSe3.

K. Prasai, P. Biswas and D. A. Drabold, Electrons and Phonons in Amorphous Semiconductors, Semicon. Sci. Tech. 31 073002 (2016).