A new universal theory and three basic rules for how defects in semiconductors behave in response to strain could lead to improvements in the electronic properties of a wide range of semiconducting materials. The work, which began with the discovery of a key physical quantity that describes how a semiconductor’s volume changes in the presence of impurities, could help researchers determine the “right” amount of strain to apply, and thus optimize the effects of these impurities.

Most materials contain impurities, or dopants, that are either intentionally or unintentionally introduced into the system – for example, during the growth of a crystal. These impurities induce volume changes in their immediate vicinity, thus producing a strain in the material.

In the latest work, researchers led by Bing Huang of Beijing Normal University’s Department of Physics and the Beijing Computational Science Research Center demonstrate that the extent of these volume changes, Δ𝑉, depends on whether the defect is positively- or negatively-charged. More precisely, Huang and colleagues show that volume increases for more negatively-charged defects and decreases for more positively-charged ones; in other words, Δ𝑉 is positive when an electron is added to the defect site and negative when an electron is removed from it.

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