|
Title
|
|
|
|
Ovonic threshold-switching GexSey chalcogenide materials : stoichiometry, trap nature, and material relaxation from first principles
| |
|
Author
|
|
|
|
| |
|
Abstract
|
|
|
|
| Density functional theory simulations are used to identify the structural factors that define the material properties of ovonic threshold switches (OTS). They show that the nature of mobility-gap trap states in amorphous Ge-rich Ge50Se50 is related to Ge-Ge bonds, whereas in Se-rich Ge30Se70 the Ge valence-alternating-pairs and Se lone-pairs dominate. To obtain a faithful description of the electronic structure and delocalization of states, it is required to combine hybrid exchange-correlation functionals with large unit-cell models. The extent of localization of electronic states depends on the applied external electric field. Hence, OTS materials undergo structural changes during electrical cycling of the device, with a decrease in the population of less exothermic Ge-Ge bonds in favor of more exothermic Ge-Se. This reduces the amount of charge traps, which translates into coordination changes, an increase in mobility-gap, and subsequently changes in the selector-device electrical parameters. The threshold voltage drift process can be explained by natural evolution of the nonpreferred Ge-Ge bonds (or "chains"/clusters thereof) in Ge-rich GexSe1-x. The effect of extrinsic doping is shown for Si and N, which introduce strong covalent bonds into the system, increase both mobility-gap and crystallization temperature, and decrease the leakage current. |
| |
|
Language
|
|
|
|
English
| |
|
Source (journal)
|
|
|
|
Physica status solidi: rapid research letters. - Berlin
| |
|
Publication
|
|
|
|
Weinheim
:
Wiley-v c h verlag gmbh
,
2020
| |
|
ISSN
|
|
|
|
1862-6254
| |
|
DOI
|
|
|
|
10.1002/PSSR.201900672
| |
|
Volume/pages
|
|
|
|
10 p.
| |
|
Article Reference
|
|
|
|
1900672
| |
|
ISI
|
|
|
|
000512431100001
| |
|
Medium
|
|
|
|
E-only publicatie
| |
|
Full text (Publisher's DOI)
|
|
|
|
| |
|
Full text (publisher's version - intranet only)
|
|
|
|
| |
|