A method for fabricating a semiconductor device includes generating a wafer by generating an N-type semiconductor layer and an active region on the N-type semiconductor layer. The N-type semiconductor layer is located on a first side of the active layer. One or more oxidizing layers are generated along with a P-type semiconductor layer generated on a second, opposite side of the active layer. The wafer is etched to expose a surface of each oxidizing layer. Oxidation of a first region of each oxidizing layer is allowed, where a second region of each oxidizing layer remains non-oxidized.