1. A crossbar structure comprising: a first layer or layers including at least one first p-type region and at least one first n-type region; a second layer or layers including at least one second p-type region and at least one second n-type region; and a resistance programmable material formed between the first layer(s) and the second layer(s), wherein the first layer(s) and the second layer(s) include first and second intersecting wiring portions forming a crossbar array, wherein the first layer(s) comprise a first rectification layer having the first p-type region and first n-type region and having a first array of input wires on one side of the first rectification layer and a first array of output wires on an opposite side of the first rectification layer and the second layer(s) comprise a second rectification layer having the second p-type region and second n-type region and having a second array of input wires on one side of the second rectification layer and a second array of output wires on an opposite side of the second rectification layer, wherein the first array of input wires is not parallel to the first array of output wires and the second array of input wires is not parallel to the second array of output wires.