AbstractsPhysics

GaAs1-xBix is a new III-V semiconductor alloy that shows promise for many optoelectronic applications. In this thesis, several characterization techniques were used to explore the properties of molecular beam epitaxy grown GaAs1-xBix alloys in a wide range of Bi-content. The fundamental bandgap and the optical absorption coefficient of pseudomorphic GaAs1-xBix/GaAs films are studied by optical transmission and photoluminescence spectroscopies. All GaAs1-xBix films (0≤x≤17.8%) show direct optical bandgaps. The bandgap (Eg) decreases strongly with increasing Bi-content, reaching 0.52 eV (~2.4 µm) at 17.8% Bi. At Eg <1.06 eV, GaAs1-xBix has the least lattice mismatch from GaAs of any ternary GaAs alloy, including GaAsN, for a given bandgap. Below the GaAs1-xBix bandgap, exponential absorption tails are observed with Urbach energies 3-6× larger than that of bulk GaAs. The electrical conductivity and Hall transport measurements on nominally undoped GaAs1-xBix films with 0