Thermal conductivity of gallium arsenic nitride (GaAsN) epilayer on gallium arsenide (GaAs) substrate prepared by molecular beam epitaxy technique was measured using pulsed photothermal reflectance technique. Three-layer model incorporated thermal boundary resistance was applied to extract the thermal properties from the sample's photothermal response. Within the thickness ranging from 20 to 80 nm, no thickness dependent relationship with thermal conductivity of GaAsN epilayer was found, and the average thermal conductivity is approximately 27 W/mK at room temperature. The thermal boundary resistance at the Au/GaAsN interface is in the order of 10(-8) m(2) K/W. (C) 2003 Elsevier B.V. All rights reserved.