High resolution EELS study of novel semiconductor alloys: Ge$_{1-x-y}$Si$_{x}$Sn$_{y}$ and AlPSi$_{3}$

Metastable alloys play a fundamental role in modern semiconductor science and technology as a major tool for band gap and strain engineering. When these alloys incorporate highly dissimilar materials, such as Si and Sn in Ge$_{1-x-y}$Si$_{x}$Sn$_{y}$ alloys or III-V pairs in group-IV matrices, as in the new (III-V)$_{x}$(IV)$_{5-2x}$ systems synthesized by our group, the atomic distribution at the sub-nanometer scale is of paramount concern, since even slight deviations from randomness or from predicted ordered structures can have a dramatic impact on the electronic structure. Aberration-corrected microscopes provides the opportunity to generate atom-selective images with unprecedented structural and chemical detail. For this work, we used Electron Energy Loss Spectroscopy (EELS) to map the Sn distribution in Ge$_{1-y}$Sn$_{y}$ and Ge$_{1-x-y}$Si$_{x}$Sn$_{y}$ alloys, as well as the distribution of Al and P atoms in AlPSi$_{3}$ to elucidate local bonding configurations and atom substitutionality. The EELS measurements also provide information on the electronic structure, which is compared with optical results and theoretical calculations.