SPEAKER: Kirstin Alberi, NREL
TITLE: Localization in Dilute Semiconductor Alloys
ABSTRACT: Dilute GaAs1-xNx and GaAs1-xBix semiconductor alloys are promising materials for high efficiency multijunction solar cells and light emitting diodes due to the unique evolution of their optical and electronic properties with composition. While N and Bi are both isoelectronic impurities in GaAs, their much larger/smaller electronegativity than As causes them to introduce localized states that interact with the host electronic structure. The resulting changes have been found to be beneficial for bandgap engineering but at the cost of increased carrier localization. Understanding the evolution of carrier localization behavior, the resulting properties of so-called “highly mismatched” alloys and the ways in which they can be tuned is critical for continued material engineering efforts. I will present insights into the nature of N and Bi pair and cluster states in GaAs, impurity band formation and their potential impact on the functionality of the alloy. I will also present our work on the development of light-stimulated molecular beam epitaxy to synthesize these materials.
HOST: James Williams