Thermal characteristics in infrared emitter elements studied by Raman scattering

Thermal characteristics of heavy-boron-doped Si resistor micro-bridge in infrared (IR) emitters, or so-called IR image simulators, have been studied with the micro-Raman scattering measurement. By illuminating the Si bridge using microscope-objective-focused intensive laser power and taking the advantage of the suspension nature of the Si bridge, the shone spot has been heated up, resulting in changes in Raman spectrum. By taking into account of Fano interference between the inter-valence-band transitions and the optical phonons, the line-shape of the recorded Si Raman spectrum has been analyzed, yielding the Raman peak position and the intensity ratio of the Stokes to anti-Stokes scatterings. The temperature of the measured point has been calculated using these parameters. Line-scanning Raman measurement along some typical directions and Raman mapping over the complete surface of the Si bridge have been performed and the temperature of each measured point has been determined. Because the boundary conditions are different at different places, the same laser illumination leads to different elevated temperature, revealing the heat conduction capabilities at different parts of the Si bridge. The temperature distribution over the Si bridge has been schematically displayed. A finite element simulation analysis has also been carried out and compared with the experimental data. While the thermal characteristics concluded by the simulation are symmetric and uniform, the experimental results, in addition to the agreement to the calculated ones in general, give some case-dependent information, which is more important to reflect the features of actual devices and provides the basis for device design and optimization.