Characterizing the layer properties of AlGaAs/GaAs heteroface solar cell structures by specular spectral reflectance

A cheap and non-destructive method for characterizing wafers prior to, during, and after processing is presented. This method is based on optical reflectance measurements. Its application to AlGaAs/GaAs heteroface solar cell structures allows the determination of the thickness of both the cap and window layers, the aluminum composition (even if it is graded) of the window layer and both the thickness and composition of surface oxide (if any). The feasibility of the procedure and method here presented is demonstrated by applying it to two kinds of structures grown by MOCVD (metal organic chemical vapor deposition) and LPE (liquid phase epitaxy). The results obtained are validated experimentally by SIMS and Raman. Finally, the influence of several calculation parameters on the final result is analyzed.