Probing the Unique Role of Gallium in Amorphous Oxide Semiconductors through Structure-Property Relationships
This study explores the unique role of Ga in amorphous (a-) In–Ga--O oxide semiconductors through combined theory and experiment. It reveals substitutional effects that have not previously been attributed to Ga, and that are investigated by examining how Ga influences structure—property relationships in a series of pulsed laser deposited a-In–Ga--O thin films. Element-specific structural studies (X-ray absorption and anomalous scattering) show good agreement with the results of ab initio molecular dynamics simulations. This structural knowledge is used to understand the results of air-annealing and Hall effect electrical measurements. The crystallization temperature of a-IO is shown to increase by as much as 325 °C on substituting Ga for In. This increased thermal stability is understood on the basis of the large changes in local structure that Ga undergoes, as compared to In, during crystallization. Hall measurements reveal an initial sharp drop in both carrier concentration and mobility with increasing Ga incorporation, which moderates at > 20 at% Ga content. This decline in both the carrier concentration and mobility with increasing Ga is attributed to dilution of the charge-carrying In--O matrix and to increased structural disorder. The latter effect saturates at high at% Ga.
S. L. Moffitt and Q. Zhu and Q. Ma and A. F. Falduto and D. B. Buchholz and R. P. Chang and T. O. Mason and J. E. Medvedeva and T. J. Marks and M. J. Bedzyk, "Probing the Unique Role of Gallium in Amorphous Oxide Semiconductors through Structure-Property Relationships," Advanced Electronic Materials, vol. 3, no. 10, Blackwell Publishing Ltd, Oct 2017.
The definitive version is available at https://doi.org/10.1002/aelm.201700189
Center for High Performance Computing Research
Keywords and Phrases
amorphous semiconductors; conductivity; local structure; oxides
International Standard Serial Number (ISSN)
Article - Journal
© 2017 Blackwell Publishing Ltd, All rights reserved.
01 Oct 2017
This work was supported by the NSF MRSEC Program No. DMR 1121262 at the Materials Research Center of Northwestern University (NU).