Surface Charge Analysis is, broadly speaking, an alternative to traditional CV technology.  In CV, one determines depletion depth by measuring the capacitance of the series combination of an oxide layer and the depletion region, while varying the depletion depth by changing the voltage between the substrate and an electrode at the surface of the oxide.  Surface Charge Analysis measures the depletion depth directly, via an optical technique, as it varies the depletion depth similar to CV.