- In this work a novel method to characterize quantum well (QW) structures and devices is presented. The method is based on the well-known surface photovoltage spectroscopy (SPS) and on numerical simulations. It is shown that the surface photovoltage is sensitive to the electron hole energy transition levels in the well layer as well as to features of other regions of the structure. The photovoltaic response as function of well width is numerically studied and is found to increase with decreasing well width. As a result of the spectra analysis growth parameters such as quantum well width and ternary layer composition (both of quantum well and cladding layers) are accurately determined. In addition, structure properties such as electric fields and effective carriers lifetime at the well are estimated. Finally it is shown that operating device parameters such the lasing wavelength may also be obtained. The results demonstrate the power of SPS as a characterization method for QW structures and devices in a contactless and non-destructive manner.