A heterostructure for an optoelectronic device is disclosed. The heterostructure includes an active region including at least one quantum well and at least one barrier and an electron blocking layer located adjacent to the active region, wherein the electron blocking layer includes a region of graded composition. An asymmetric p-type superlattice layer is located adjacent to the electron blocking layer, wherein the p-type superlattice includes at least one superlattice period comprising a set of wells and a set of barriers. A thickness of at least one of: each well in the set of wells or each barrier in the set of barriers varies along a length of the p-type superlattice.