Barrier breakdown mechanism in nano-scale perpendicular magnetic tunnel junctions with ultrathin MgO barrier

Hua Lv, Diana C. Leitao, Zhiwei Hou, Paulo P. Freitas, Susana Cardoso, Thomas Kämpfe, Johannes Müller, Juergen Langer, Jerzy Wrona

Research output: Contribution to journalArticleAcademicpeer-review

14 Citations (Scopus)

Abstract

Recently, the perpendicular magnetic tunnel junctions (p-MTJs) arouse great interest because of its unique features in the application of spin-transfer-torque magnetoresistive random access memory (STT-MRAM), such as low switching current density, good thermal stability and high access speed. In this paper, we investigated current induced switching (CIS) in ultrathin MgO barrier p-MTJs with dimension down to 50 nm. We obtained a CIS perpendicular tunnel magnetoresistance (p-TMR) of 123.9% and 7.0 Ω·μm2 resistance area product (RA) with a critical switching density of 1.4×1010 A/m2 in a 300 nm diameter junction. We observe that the extrinsic breakdown mechanism dominates, since the resistance of our p-MTJs decreases gradually with the increasing current. From the statistical analysis of differently sized p-MTJs, we observe that the breakdown voltage (Vb) of 1.4 V is 2 times the switching voltage (Vs) of 0.7 V and the breakdown process exhibits two different breakdown states, unsteady and steady state. Using Simmons' model, we find that the steady state is related with the barrier height of the MgO layer. Furthermore, our study suggests a more efficient method to evaluate the MTJ stability under high bias rather than measuring Vb. In conclusion, we developed well performant p-MTJs for the use in STT-MRAM and demonstrate the mechanism and control of breakdown in nano-scale ultrathin MgO barrier p-MTJs.

Original languageEnglish
Article number055908
Pages (from-to)1-6
Number of pages6
JournalAIP Advances
Volume8
Issue number5
DOIs
Publication statusPublished - 1 May 2018
Externally publishedYes

Bibliographical note

Funding Information:
H. Lv acknowledge FCT grant: SFRH/BD/93597/2013. This project has received funding from the Electronic Component Systems for European Leadership Joint Undertaking under grant agreement No. 692519. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation program and Belgium, Germany, France, Netherlands, Poland, United Kingdom. D. C. Leitao acknowledges financial support through FSE/POPH. Z. Hou acknowledges the National Natural Science Foundation of China under Grants No. 51201059, Natural Science Foundation of Henan province No. 14A140027 and the Fund of HAUT No. 171208.

Funding Information:
H. Lv acknowledge FCT grant: SFRH/BD/93597/2013. This project has received funding from the Electronic Component Systems for European Leadership Joint Undertaking under grant agreement No. 692519. This Joint Undertaking receives support from the European Union's Horizon 2020 research and innovation program and Belgium, Germany, France, Netherlands, Poland, United Kingdom. D. C. Leitao acknowledges financial support through FSE/POPH. Z. Hou acknowledges the National Natural Science Foundation of China under Grants No. 51201059, Natural Science Foundation of Henan province No. 14A140027 and the Fund of HAUT No. 171208.

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