semiconductors*

Substituting Bi anions in place of As allows for effective tuning of the energy band gap
of GaBi_xAs_1-x. Such band gap control has applications in spintronics (quantum
computing) and optoelectronics (photovoltaics). The energy band gap of dilute GaBi_xAs_1-x alloys is dependent on the alloy configuration, in addition to the alloy concentration. In
order to explore the effects of Bi configuration in dilute GaBi_xAs_1-x alloys, an atomistic,
nearest-neighbor, sp³s* tight-binding Hamiltonian is used to determine the
energy levels for statistically constructed alloy supercells with random, clustered,
and gaussian weighted distributions . By correlating these energies to both qualitative
and quantitative measures of Bi clustering, the effects of Bi clustering are explored.
From our theoretical calculations, we show that increases in Bi clustering correlate with
greater decrease in band gap energies. Additionally, in more densely clustered
configurations, we see higher total Bi probability for hole states and faster Bi band
broadening congruent with the band anti-crossing model for GaBi_xAs_1-x.