Giant bowing of the band gap and spin-orbit splitting energy in GaPBi dilute bismide alloys.

Using spectroscopic ellipsometry measurements on GaPBi/GaP epitaxial layers up to x = 3.7% we observe a giant bowing of the direct band gap ([Formula: see text]) and valence band spin-orbit splitting energy (Δ). [Formula: see text] (Δ) is measured to decrease (increase) by approximately 200 meV (240 meV) with the incorporation of 1% Bi, corresponding to a greater than fourfold increase in Δ in going from GaP to GaPBi.