Theoretical study of the effects of isovalent coalloying of Bi and N in GaAs

GaAs1-xNx alloys have unique properties among the III-V systems to simultaneously lower both the lattice constant and the band gap. Therefore, it has a strong potential for optoelectronic device applications. However, due to the large size mismatch between N and As, the growth of high-quality GaAsN alloy on GaAs substrates is difficult. To overcome this problem, we propose here a material, the GaAs1-x-yNxBiy alloy, which can be lattice matched to GaAs with the appropriate ratio between the concentration of Bi and N (y=1.7x). Based on band structure and total-energy calculations we show that coalloying of Bi and N in GaAs lowers the alloy-formation energy and drastically reduces the amount of N needed to reach the 1-eV band gap, which is important for high-efficiency solar cell and infrared-laser applications.