A device for producing electricity. The device comprises an indium gallium phosphide semiconductor material comprising a plurality of indium gallium phosphide material layers each layer having different dopant concentrations and doped with either n-type dopants or p-type dopants, a first terminal on a first surface of the semiconductor material, a beta particle source proximate the first surface for emitting beta particles that penetrate into the semiconductor material, and a second terminal on a second surface of the semiconductor material; the semiconductor material for producing current between the first and second terminals responsive to the beta particles penetrating into the semiconductor material.