TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The content of the gallium dopant for the silicon raw material is 5x10-4-6.3x1-2 atm%. The oxygen content of the polycrystalline silicon is 1x1016-1x1018/cm3. Preferred Condition: The cooling rate for the melted silicon raw material is less than or equal to1degreesC/min. Preferred Method: Oxygen-including compound is added to the silicon raw material, in addition to the gallium dopant. Preferred Material: The oxygen-including compound is silicon oxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The content of the gallium dopant for the silicon raw material is 5x10-4-6.3x1-2 atm%. The oxygen content of the polycrystalline silicon is 1x1016-1x1018/cm3. Preferred Condition: The cooling rate for the melted silicon raw material is less than or equal to1degreesC/min. Preferred Method: Oxygen-including compound is added to the silicon raw material, in addition to the gallium dopant. Preferred Material: The oxygen-including compound is silicon oxide. EXAMPLE - Silicon raw material (4.5 kg) and gallium metal (0.25 g) were charged into a quartz crucible whose inner surface was coated with a mold lubricant. The mixture was heated to 1550degreesC under argon (Ar) gas atmosphere to melt the silicon raw material. After the melting, the crucible was cooled down at 1degreesC/min to crystallize the melted silicon raw material. The resultant crystalline silicon ingot was cut off, and the cross section of the silicon ingot was observed. Results showed that in the silicon ingot, polycrystalline boundaries were created vertically and silicon crystals were created in columnar. The polycrystalline silicon ingot was cut off with a wire saw to make a substrate with a thickness of 300 microns. The resistivity of the polycrystalline silicon ingot was 1-2 Omegacm, and decreased in the upper portion of the silicon. The substrate was immersed into nitric acid (HNO3)/nitrogen fluoride (NF) solution to etch the surface of the substrate in mirror to remove slice damaged layer formed at the substrate surface. The substrate was immersed into iodine ethanol solution so that the surface of the substrate was chemically passivated. A simulated sunlight was irradiated onto the substrate for 2.5 hours by an optical conductivity attenuating method using microwave to measure the minority-carrier lifetime of the substrate. The minority-carrier lifetime was 42 microseconds for before and after light irradiation with gallium as the dopant species.