Abstract: The present invention provides a current blocking structure for electronic devices, preferably optoelectronic devices. The current blocking structure comprises a semiconductor material arrangement comprising an n-type ruthenium doped indium phosphide (Ru—InP) layer and a first p-type semiconductor material layer wherein the n-type Ru—InP layer is less than 0.6 ?m thick. The semiconductor material arrangement and p-type semiconductor material layer form a current blocking p-n junction. The current blocking structure may further comprise other n-type layers and/or multiple n-type Ru—InP layers and/or intrinsic/undoped layers wherein the n-type Ru—InP layers may be thicker than 0.6 ?m.