Conditions are investigated for the injection of arsenic into gallium nitride layers grown by metal-organic vapor-phase epitaxy. It is shown that the deposition of GaAs on a GaN surface relieves stresses in the GaN layer. The high-temperature overgrowth of a thin GaAs layer by a GaN layer causes As atoms to diffuse into the GaN, produces a thick, homogeneously doped GaN:As region, and creates a bright band in the photoluminescence spectrum with a maximum at similar to 2.5 eV. (C) 1999 American Institute of Physics. [S1063-7826(99)00707-3].