Diffusion of indium in single crystal zinc oxide: a comparison between group III donors

• Published in: Semiconductor science and technology Vol. 34; no. 2; pp. 25011 - 25016
• Main Authors: Sky, T N, Johansen, K M, Frodason, Y K, Aarholt, T, Riise, H N, Prytz, Ø, Svensson, B G, Vines, L
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.02.2019
• Subjects: diffusion; impurities; semiconductor; ZnO
• ISSN: 0268-1242; 1361-6641
• DOI: 10.1088/1361-6641/aafa4c

Dopant diffusion of indium (In) in single crystal zinc oxide is studied by secondary ion mass spectrometry and is interpreted using a reaction-diffusion model that invokes predictions from density functional theory (DFT). An apparent activation energy of 2.2 eV is obtained for the diffusion of In, when the local Fermi-level position is about 0.2 eV below the conduction band edge. The diffusion of In is found to be significantly faster that that reported for the other group III donors, aluminum and gallium, with several orders of magnitude higher effective diffusivities, that can be assigned to a lower migration barrier for the diffusion of In. Furthermore, our results reveal self-consistency in previous DFT results of defect formation- and migration energies. From this, the diffusion of In is suggested to occur through mobile charged zinc vacancies V Zn 2 − that form intermediate mobile ( In Zn V Zn )− pairs. The pairs in turn dissociate rather readily at the studied temperatures (850 °C-1150 °C), which results in distinct and abrupt diffusion fronts for the In depth distribution profiles.