Isoelectronic As doping effects on the optical characteristics of GaN films grown by metalorganic chemical-vapor deposition

We have studied the As doping effects on the optical characteristics of GaN films by time-integrated photoluminescence and time-resolved photoluminescence. When As is incorporated into the film, the localized defect levels and donor-acceptor pair transition become less resolved. The recombination lifetime of neutral-donor-bound exciton (I₂) transition in undoped GaN increases with temperature as T^1.5. However, the I₂ recombination lifetime in As-doped GaN first decreases exponentially from 98 to 41 ps between 12 and 75 K, then increases gradually to 72 ps at 250 K. Such a difference is related to the isoelectronic As impurities in GaN, which generate nearby shallow levels that dominate the recombination process.