| Abstract Scope |
Dilute bismuthides (a/k/a bismides) are a fairly new and promising material for optoelectronics and thermoelectrics in III-V semiconductors. Similar to dilute nitrides, dilute bismuthides exhibit bandgap narrowing due to band anticrossing. In contrast to dilute nitrides, however, most of the band narrowing in dilute bismuthides occurs in the valence band. It has been reported that the bandgap reduces by about 84 meV/%Bi, which is a significant reduction compared to other III-V alloys [1]. The ability to manipulate the bandgap is ideal for new narrow bandgap optoelectronic devices such as lasers and detectors. For thermoelectrics, more specifically thermoelectric power generation (TPG), dilute bismuthides show promise due to bismuth’s heavy mass and large atomic cross-section. Applications for TPGs include automobiles, solar cells, and UAVs. In the past, researchers have tried increasing ZT by increasing the thermoelectric power factor (S<SUP>2</SUP>σ) and decreasing the thermal conducitivity. Unfortunately, all of these parameters are coupled; increasing the electrical conductivity (σ) decreases the Seebeck coefficient (S) while increasing the thermal conductivity (κ) and vice-versa. The incorporation of nanoparticles into materials has been shown to reduce the thermal conductivity passed the alloy limit due to phonon scattering. Most of the research done in the dilute bismuthide community has been focused on incorporating bismuth into GaAs and finding the ideal growth conditions. Previous work has shown that greater than 10% Bi incorporation is achievable [2][3]. However, there is relatively limited research done on incorporating bismuth into InGaAs, particularly lattice-matched to InP. We present and discuss our progress on epitaxially-grown InGaBiAs on InP (both lattice matched and mismatched) by molecular beam epitaxy. We consider the effects of growth conditions (specifically, substrate temperature, As/III ratio, and Bi flux) on the bismuth incorporation. We also explore the electrical, optical, and structural properties of the films using Hall Effect, spectrophotometry, and x-ray diffraction. Finally, we consider the prospects of these materials for both optoelectronic and thermoelectric devices. |