Alloys and Exotic Materials

The chapter describes how the band parameters of ternary and quaternary alloys can be interpolated over the entire range of compositions, and tabulate the non-vanishing bowing parameters for most of the common alloys with both zinc-blende and wurtzite lattice structure. It also describes ordering in some of the ternary alloys, and how ordering affects the energy gap. The band parameters of dilute nitrides, dilute bismides, and hexagonal boron nitride are also examined. Finally, the chapter presents schemes for interpolating the optical parameters of III–V alloys, i.e., the real and imaginary parts of the permittivity or dielectric function.

Plasmon-assisted bandgap engineering in dilute nitrides

The inherent ability of plasmonic bowtie nanoapertures (NAs) to localize the electromagnetic field at a subwavelength scale was exploited to engineer the H removal process in dilute nitrides at the nanometer level. Dilute nitride semiconductor alloys (e.g. GaAsN with a small percentage of nitrogen) are characterized by peculiar optoelectronic properties and, most importantly, by an even more peculiar response to hydrogen incorporation. In this class of materials, it is indeed possible to tune post-growth the alloy bandgap energy by a controlled incorporation of hydrogen atoms. The formation of N-H complexes neutralizes all the effects N has on the host matrix, among which is the strong narrowing of bandgap energy. In the present work, bowtie NAs resonant to the N-H complex dissociation energy were numerically modeled by finite element method simulations, realized by a lithographic approach, and characterized by scanning probe microscopy and resonant scattering spectroscopies. The conditions to get the maximum field enhancement at a specific position below the metal/semiconductor interface, namely at the dilute nitride quantum well position, were identified, demonstrating the ability to achieve a plasmon-assisted spatially selective hydrogen removal in a GaAsN/GaAs quantum well sample. Hydrogen removal through bowtie NAs turns out to be way more efficient (approximately two orders of magnitude) than through the plain surface, thus indicating that bandgap engineering through plasmonic nanostructures can be optimized for future efficient realization of site-controlled single-photon emitters and for their deterministic integration in plasmonic devices.