The facet temperature of AlGaAs ridge waveguided single-quantum-well lasers with various ridge widths and cavity lengths were measured as a function of output power and injection current using Raman microprobe spectroscopy. The facet temperature was found to scale with the injection current density rather than the photon flux. In addition, no large discontinuities were found below and above the lasing threshold, suggesting that the absorption of the emitted photons plays only a minor role in the facet heating. These data imply that the facet heating during the initial slow degradation regime is due to the surface nonradiative recombination of carriers and is primarily determined by the injection current density. This could be contrasted to the catastrophic optical damage regime where the lasing photons play a key role in the heating process.