Semiconductor light emitting device including graded region

One or more regions of graded composition are included in a III-P light emitting device, to reduce the Vf associated with interfaces in the device. In accordance with embodiments of the invention, a semiconductor structure comprises a III-P light emitting layer disposed between an n-type region and a p-type region. A graded region is disposed between the p-type region and a GaP window layer. The aluminum composition is graded in the graded region. The graded region may have a thickness of at least 150 nm. In some embodiments, in addition to or instead of a graded region between the p-type region and the GaP window layer, the aluminum composition is graded in a graded region disposed between an etch stop layer and the n-type region, or .