Electronic and optical properties of dilute Bismide alloys*

We will present photoluminescence measurements of GaAs$_{(1-x)}$Bi$_{x}$ thin films containing dilute concentration ($x \quad \le $ 0.045{\%}) of isoelectronic impurity Bi. We observe that Bi induces strong perturbation to the host band structure even at these low concentrations and see no spectral evidence for isolated Bi forming a bound state in GaAs. Very similar to the case of Bi in GaP, we observed no Bi-Bi pair states. An `undulation' spectrum is observed which we attribute to the vibronic levels of acceptors.