Advances in vibrational spectroscopy provide new ways for characterizing semiconductor impurities

Spectroscopies have been used to reveal the microscopic properties of defects and impurities in semiconductors for decades. Vibrational spectroscopy has proved to be an effective probe for detecting defects that include elements lighter than the host crystal elements. A pair of physicists from Lehigh University have co-written a tutorial on how to leverage the power of this technique to decipher properties of semiconductors with light-mass element defects.

“When a new material comes into vogue, there’s got to be a community of people that sorts out its chemistry and electronic properties,” said co-author Michael Stavola. “Vibrational spectroscopy is a key tool that provides this insight.”

Vibrational spectroscopy is a common method used to characterize semiconductor crystals, including silicon used in integrated circuits. Advances in computing power have helped bridge the gap between theoretical and experimental physics to glean new information on semiconductors, especially ones containing light-mass elements. These elements, such as hydrogen and oxygen, are among the most common elements in nature and are frequent impurities in semiconductors, both accidentally and by design.

When these impurities are introduced into semiconductors, they give rise to new, localized vibrational modes with higher frequencies than the rest of the crystal. The tutorial emphasizes that vibrational spectroscopy can be used with other semiconductor characterization methods, such as uniaxial stress and photoionization, to determine the diffusive motion of impurities and changes in charge state, respectively.

Stavola and co-author W. Beall Fowler have used vibrational spectroscopy to determine the effect of hydrogen impurities in semiconducting oxides as well as other applications, and hope the review will inform other researchers investigating impurities in semiconductors, including emerging wide and ultrawide bandgap materials.

Source: “Tutorial: Novel properties of defects in semiconductors revealed by their vibrational spectra,” by Michael Stavola and W. Beall Fowler, Journal of Applied Physics (2018). The article can be accessed at https://doi.org/10.1063/1.5011036 .