Investigation of doping effects in hafnium oxide-based non-volatile resistance-change random access memory
Abstract/Contents
- Abstract
- Computer memory is divided into a complex architecture: caches built on SRAM, main memory built on DRAM, and nonvolatile memory provided by flash or magnetic hard disks. Each memory technology has significant tradeoffs: SRAM and DRAM are fast and volatile, while flash is slower but nonvolatile. Although flash exhibits significantly faster random access times than its predecessor, magnetic hard drives, it is still much slower than DRAM, sometimes resulting in memory bottlenecks when loading large programs or databases into memory. The rise of data-centric computing has created a need for a new layer between DRAM and flash in the memory hierarchy, called storage class memory (SCM). Several new memory technologies, all based upon fundamentally different physical mechanisms, are competing to be used in the new SCM layer. One of the most promising technologies is resistance-change random access memory (RRAM). RRAM is capable of achieving the same bit densities as flash, but at lower power and higher speed. However, while RRAM has been a topic of intense research, device variability and retention remain major hurdles to widespread adoption. Many strategies have been used to try to improve these characteristics, and one of the most promising has been doping, but relatively few dopant materials have been investigated. In this work, the properties of hafnium dioxide (HfO2) RRAM devices are explored from a fundamental perspective using density functional theory (DFT). DFT is uniquely suited for achieving clarity on the quantum mechanical and materials aspects of RRAM operation. First, DFT is applied to hafnium dioxide (HfO2) to quantify the thermodynamic properties of HfO2 and their impact on RRAM device operation. Of particular interest is the connection of electronic and ionic processes, i.e. how charge trapping affects the formation and rupture of conductive filaments. These results can be used to add defect charge state to the phenomena that drive device switching, along with electric field and joule heating. In the second part of this work, the addition of hydrogen impurities to HfO2 is explored. Hydrogen has been experimentally found to improve HfO2 RRAM device properties, but a physical explanation for this improvement is lacking. It is found that the presence of hydrogen shifts the energetics and kinetics of HfO2 in a direction that is favorable for resistive switching. In the last part of this work, the hydrogen study is expanded into a study of all possible dopant species. Here, high-throughput DFT calculations are used to systematically quantify the properties of 50 different dopants. These calculations uncover the underlying trends that govern dopant behavior and predict which dopants will provide optimum device properties.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Duncan, Daniel Steven |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Nishi, Yoshio, 1940- |
| Thesis advisor | Nishi, Yoshio, 1940- |
| Thesis advisor | Magyari-Köpe, Blanka, 1973- |
| Thesis advisor | Wong, S |
| Advisor | Magyari-Köpe, Blanka, 1973- |
| Advisor | Wong, S |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Daniel Steven Duncan. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Daniel Steven Duncan
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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