Semiconductor assessment using photothermal radiometry

In conventional photothermal radiometry, a focused infrared detector is used to measure the a.c. surface temperature variations induced in a sample under periodic optical heating. Application of this technique to intrinsic silicon has led to the realisation that an alternative mechanism is responsible for IR emission from the sample. This mechanism relies upon optically generated electron-hole pairs modifying the emissive properties of the sample. A brief theoretical interpretation is given which reveals the IR emission dependence upon the electronic properties of the semiconductor. Several results are presented illustrating the potential of the technique for semiconductor material assessment. Specific applications are towards ion implant monitoring, and surface quality characterisation.