The properties of dilute bismuthides and rare-earth containing materials for applications in thermoelectrics, optoelectronics, and terahertz technology

(In)GaAs containing low concentrations of Bi are called dilute bismuthides. When Bi is incorporated, bandgap narrowing occurs because of valence band anticrossing (VBAC). The ability to tune the bandgap of this material is useful in the field of optoelectronics. Dilute bismuthides, or more specifically n-InGaBiAs, are also expected to be good thermoelectric materials because Bi is a heavy atom and the conduction band should be similar to InGaAs. This dissertation discusses the electrical and thermoelectric properties of n-InGaBiAs. This dissertation also discusses n-InGaBiAs as a potential mid-IR transparent contact material.;ErAs or TbAs nanoparticles can be embedded in GaAs or InGaAs by co-deposition via molecular beam epitaxy (MBE). These materials have interesting properties that can be applied to thermoelectrics and terahertz technologies. For thermoelectrics, the nanoparticles have a dopant-like behavior and provide scattering centers for phonons. ErAs nanoparticles in GaAs provide the short carrier lifetimes and high dark resistance that is needed for a terahertz material. An interesting question one may ask is what will happen when both Er and Tb are co-deposited. It was hypothesized that core-shell nanoparticles would form through a strain-driven process. In this dissertation, the observation of self-assembled rare-earth core-shell nanoparticles in InGaAs is presented and discussed. The core-shell nanoparticles were observed using atom probe tomography (APT). The structure consisted of mixed core and a pure TbAs shell. A simple energetics model confirms the observation of core-shell nanoparticles.