Contactless measurement of sheet resistance and mobility of inversion charge carriers on photovoltaic wafers

A new application of the differential junction photovoltage (diff-JPV) measurement technique is introduced. The technique's capability to determine the sheet resistance of charge carriers in inversion layers Rs,inv for silicon wafers coated by different dielectrics is investigated. The dielectrics - SiOx, SiNx and AlOx – used in this study are all highly relevant for photovoltaic applications, especially for inversion layer solar cell concepts. The newly developed generalized measurement routine and evaluation utilizing the phase dependent surface potential signals of the diff-JPV sensor resulted in a very rapid Rs,inv extraction even in the very high (>10 kΩ/sq.) Rs,inv range which is typical for inversion layers. However, reference inversion layer sheet resistance values can be hardly obtained without the fabrication of test devices. Thus, to validate the reliability of the diff-JPV measurement an indirect method is applied by measuring the mobility of the inversion charge carriers from the Rs,inv results after sequential surface corona charging steps. A very sharp transition of the diff-JPV results is observed showing significant signal in the inversion regime exclusively and providing Rs,inv results in the expected range. The inversion charge carrier mobility data, calculated from the Rs,inv versus surface charge plots, are consistent and comparable to those found from device tests. Sheet resistance and mobility results exhibit high sensitivity to the surface morphology (i.e, textured versus polished), the interface quality and the amount of charge within the given dielectrics. The contactless JPV is proven to be a fast and efficient way for the rapid characterization of inversion layers properties. It can even be accomplished in production lines in case of future industrialization of inversion layer based solar cell technologies. •Differential JPV measurement is proven to provide contactless and reliable determination of sheet resistance of inversion charge carriers within 1 s.•Differential JPV technique detects and qualifies inversion layers induced by fixed charges within SiNx and AlOx layers.•Accurate sheet resistance test method for cell concepts utilizing inversion layers, e.g. inversion layer solar cells, applicable even in production lines.•Differential JPV combined with corona charging provides the contactless mobility measurement of inversion charge carriers without test device fabrication.•Contactless mobility results feature high sensitivit