The effect of stress on the measured temperatures of a GaN Schottky diode is studied using micro-Raman scattering under passive and active heating. Our experiment shows that each specific heteroepitaxial structure should be calibrated independently under passive heating conditions in order to minimize significant errors in the measurement of device temperature. This error is introduced by differences in biaxial strain (resulting from differences in lattice mismatch, thermal expansion coefficient, and relaxation) between the structure under investigation and that employed for calibration. Measurements of the operating temperature of a GaN Schottky diode indicated that a large error in temperature can result from the use of a temperature calibration from a different structure. (c) 2005 The Electrochemical Society.