Broad-area optical characterization of well-width homogeneity in GaN/AlxGa1 - XN multiple quantum wells grown on sapphire wafers

We have performed spatially resolved photoluminescence spectroscopy on the entire 2 in. sapphire waters containing GaN/AlxGa1 - xN multiple quantum wells grown by metalorganic chemical vapor deposition. We have observed an energy shift of about 50 meV in the ground level emission energy between the center and the peripheric regions of the samples. We show that such a variation in the emission energy is due to a well narrowing of about 3 ML from the center to the outer regions of the wafers, which induces a large Stark shift through the built-in field.