Temperature Distributions in Ⅲ-Ⅴ and SiC Micro-Wave Power Transistors Using Spatially Resolved Photoluminescence and Raman- Spectrometry Mapping Respectively

摘要

This paper describes a new method for the mapping of local temperatures in the active region of high-power Ⅲ-Ⅴ semiconductor transistors for microwave applications. The measurement technique involves scanning a focused laser beam at the surface of a chip inside its package, while the photo-luminescence (PL) or the Raman spectra produced are recorded sequentially for each position of the laser beam. The local temperature is deduced either from the corresponding wavelength shift of the PL (which represents changes in the band-gap due to heating) or from Raman Stokes peak shift or from the Stokes to anti-Stokes intensity ratio (which correspond to changes in optical phonon frequencies and population respectively due to heating). Results are shown both for SiC-based field effect transistors and for bipolar type transistors (heterojunction bipolar transistors ― HBTs ― in the GaAs/Ga_(1-x)In_xP system). A spatial resolution of 1 μm and an accuracy in the temperature determination of +- 3 °C are demonstrated, especially for the HBTs. Finally, procedures are proposed to implement the information on local operating temperatures provided by this method into thermal resistance calculations.