Effect of nitrogen pressure on the composition and structure of thin films GaAs$_{1-x-y}$N$_x$Bi$_y$

Thin films of GaAs$_{1-x-y}$N$_x$Bi$_y$ were deposited on a GaAs (100) substrate by pulsed laser deposition using an argon-nitrogen gas mixture at a pressure ranging from 1 to 60 Pa. The film thickness is found to decrease from 527 to 127 nm as the pressure of the argon-nitrogen gas mixture increased from 20 Pa to 60 Pa due to reflection and scattering of the plasma torch flow on nitrogen and argon atoms. The increase in pressure results in a significant decrease in the size and density of droplets on the film surface. All samples exhibit a polycrystalline structure, and the film obtained at a pressure of 60 Pa exhibits the highest crystalline perfection. The VASP software package was used to calculate theoretically the diffractogram for a (2$\times$2$\times$2) GaAs$_{0.889}$N$_{0.037}$Bi$_{0.074}$ supercell, and it has been observed that the width at half maximum intensity for the GaAsNBi (004) reflection decreases with increasing pressure of the argon-nitrogen gas mixture. The nitrogen concentration in the thin film is found to increase linearly with the increase in the pressure of the argon-nitrogen gas mixture, which was established using X-ray diffraction and photoluminescence methods. The composition of the film obtained at a pressure of 60 Pa is determined to be GaAs$_{0.957}$N$_{0.012}$Bi$_{0.021}$.