1. A composite metal oxide semiconductor, characterized in that the composite oxide semiconductor is a rare-earth oxide doped metal oxide; wherein the metal oxide is indium gallium oxide or indium gallium zinc oxide; the rare-earth oxide is praseodymium oxide; a doping molar ratio of praseodymium to the indium and gallium or indium and gallium and zinc of the metal oxide is in a range from 0.10:1 to 0.4:1; there are recombination centers for photo-induced carriers in the composite metal oxide semiconductor, wherein when the metal oxide is indium gallium zinc oxide, a molar ratio of indium and gallium and zinc complies with the formulas In/(In+Zn)≥0.76 and 0<Ga/In≤0.8, and when the metal oxide is indium gallium oxide, a molar ratio of indium and gallium is in a range from 5:1 to 5:4, wherein the doping molar ratio of praseodymium to the indium and gallium or indium and gallium and zinc of the metal oxide is in a range from greater than 0.25:1 to less than or equal to 0.4:1.
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