This finding inspired the researchers to investigate so-called superlattice structures, in which atomically thin layers of ScN and AlN are alternately deposited, an approach that can be experimentally implemented using sophisticated growth techniques. They found that precisely oriented layer structures do indeed offer significant enhancements in electro-optic properties.
Intriguingly, the scientists also realized that strain can be exploited to tune the properties close to the “Goldilocks” point, where the largest electro-optic enhancements are obtained. Strain can result from externally applied stress, or it can be built into the material through carefully designed microstructures, now a routine approach in silicon technology. Careful strain tuning could yield an electro-optic effect in AlScN that is up to an order of magnitude greater than in lithium niobate, the current go-to material.
“We are excited about the potential of AlScN to push the boundaries of nonlinear optics,” said Van de Walle. “Equally importantly, the insights reaped from this study will allow us to systematically investigate other so-called heterostructural alloys that may feature even better performance.”
The research was supported by the Army Research Office and by SUPREME, a Semiconductor Research Corporation program sponsored by the Defense Advanced Research Projects Agency.