A method of constructing a solid-state energy-density micro radioisotope power source device. In such embodiments, the method comprises depositing the pre-voltaic semiconductor composition, comprising a semiconductor material and a radioisotope material, into a micro chamber formed within a power source device body. The method additionally includes heating the body to a temperature at which the pre-voltaic semiconductor composition will liquefy within the micro chamber to provide a liquid state composite mixture. Furthermore, the method includes cooling the body and liquid state composite mixture such that liquid state composite mixture solidifies to provide a solid-state composite voltaic semiconductor, thereby providing a solid-state high energy-density micro radioisotope power source device.