A bulk loader conveys articles in bulk and has a hopper configured for receiving the articles, such as railroad articles. The epitaxial layer has a threading dislocation density of less than 107 cm2 and an in-plane lattice constant that is different from that of the first substrate and a second substrate on which the epitaxial layer is fabricated. The first memory is larger than the second memory; and the memory locations in the first memory are arranged in blocks having a plurality of different sizes.