A method for fabricating an optical modulator includes forming n-type layer, a first oxide portion on a portion of the n-type layer, and a second oxide portion on a second portion of the n-type layer, patterning a first masking layer over the first oxide portion, portions of a planar surface of the n-type layer, and portions of the second oxide portion, implanting p-type dopants in the n-type layer to form a first p-type region and a second p-type region, removing the first masking layer, patterning a second masking layer over the first oxide portion, a portion of the first p-type region, and a portion of the n-type layer, and implanting p-type dopants in exposed portions of the n-type layer, exposed portions of the first p-type region, and regions of the n-type layer and the second p-type region disposed between the substrate and the second oxide portion.