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Alternatives to aluminum gates for silicon quantum devices: Defects and strain



Ryan Stein, Zachary Barcikowski, Sujitra Pookpanratana, Joshua M. Pomeroy, Michael Stewart


Gate-defined quantum dots (QD) benefit from the use of small grain size metals for gates materials because it aids in shrinking the device dimensions. However, it is not clear what differences arise with respect to process-induced defect densities and inhomogeneous strain. Here, we present measurements of fixed charge, Qf, and interface trap density, Dit, as a function of forming gas anneal temperature for Al, Ti/Pd, and Ti/Pt gates. We also investigate the concomitant effect of these anneals on the intrinsic film stress, σ, and the coefficient of thermal expansion, α. We show Dit is minimal at an anneal temperature of 350⁰C for all materials but Ti/Pd and Ti/Pt have higher Qf and Dit compared to Al. In addition, σ and α increase with anneal temperature for all three metals with α larger than the bulk value. These results indicate that there is a tradeoff between minimizing defects and minimizing the impact of strain in quantum device fabrication.
Journal of Applied Physics


Stein, R. , Barcikowski, Z. , Pookpanratana, S. , Pomeroy, J. and Stewart, M. (2021), Alternatives to aluminum gates for silicon quantum devices: Defects and strain, Journal of Applied Physics, [online],, (Accessed May 21, 2024)


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Created September 15, 2021, Updated November 29, 2022