Direct observation of dopant atom diffusion in a bulk semiconductor crystal enhanced by a large size mismatch

Ryo Ishikawa, Rohan Mishra, Andrew R. Lupini, Scott D. Findlay, Takashi Taniguchi, Sokrates T. Pantelides, Stephen J. Pennycook

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95 Scopus citations

Abstract

Diffusion is one of the fundamental processes that govern the structure, processing, and properties of materials and it plays a crucial role in determining device lifetimes. However, direct observations of diffusion processes have been elusive and limited only to the surfaces of materials. Here we use an aberration-corrected electron microscope to locally excite and directly image the diffusion of single Ce and Mn dopants inside bulk wurtzite-type AlN single crystals, identifying correlated vacancy-dopant and interstitial-dopant kick-out mechanisms. Using a 200 kV electron beam to supply energy, we observe a higher frequency of dopant jumps for the larger and heavier Ce atoms than the smaller Mn atoms. These observations confirm density-functional-theory-based predictions of a decrease in diffusion barrier for large substitutional atoms. The results show that combining depth sensitive microscopy with theoretical calculations represents a new methodology to investigate diffusion mechanisms, not restricted to surface phenomena, but within bulk materials.

Original languageEnglish
Article number155501
JournalPhysical Review Letters
Volume113
Issue number15
DOIs
StatePublished - Oct 6 2014

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