Contact structures and methods for forming such contact structures are disclosed. An example contact structure includes a layer of semiconductor material having an interface and an electrical contact at the interface of the layer of semiconductor material, where the electrical contact includes a granular metal. An example method for forming a contact structure includes providing a substrate and producing a granular metal on at least part of the substrate, where the granular metal includes a cluster of metal islands extending essentially in a two-dimensional plane. The method further includes depositing a layer of a semiconductor material on top of the substrate and the cluster of metal islands.