We review successful measurement techniques for the evaluation of the recombination properties in semiconductor materials based on the optically induced free carrier absorption. All the methodologies presented share the common feature of exploiting a laser beam to excite electron-hole pairs within the volume of the sample under investigation, while the probing methods can vary according to the different methodology analyzed. As recombination properties are of paramount importance in determining the properties of semiconductor devices (i.e, bipolar transistor gain, power devices switching features, and solar cells efficiency), their knowledge allows for better understanding of experimental results and robust TCAD simulator calibration. Being contactless and applicable without any particular preparation of the sample under investigation, they have been considered attractive to monitor these parameters inline or just after production of many different semiconductor devices. 1. Introduction The minority carriers recombination lifetime is one of the most important parameters as it both characterizes the semiconductor materials and it strongly influences devices properties. As more than 95% of all the produced electronic devices are fabricated through CMOS process, nowadays the majority of the studies on recombination lifetime concerns power electronics, diodes, IGBTs—where lifetime killing methodologies are mostly employed—or solar cells, where recombination parameters are directly related to the conversion capability of these devices. Solar cells, without doubt, occupy an important role in the energy worldwide scenario, so the industry and research interest in their production and characterization are increasing. As said, their efficiency in converting the energy from solar to electrical critically depends on the recombination process by means of two parameters: the bulk recombination lifetime , which accounts for the recombination of electrons and holes inside the silicon crystal, and the surface recombination velocity which is strongly dependent on the interface between the material and its boundaries: the former accounts for material quality, while the latter usually depends on the fabrication process. These parameters are strongly related to the presence of defects within the semiconductor forbidden gap (which directly affects devices performance) and to the surface quality. They also depend on the semiconductor growth technique, on the doping, on the surface condition, and on the free carrier density injected in the material under operating conditions.
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