Low Temperature Photoluminescence Study of Uranium Implanted into III-V Semiconductors and AlGaAs.

摘要

Actinides, like lanthanides, have a partially filled inner shell (5f for actinides) so that semiconductors implanted with these elements should have sharp emissions characteristic of the atomic transitions of the free element ions. In this work, II-V semiconductors Gallium Arsenide, Gallium Phosphide, and Indium Phosphide and ternary Al(0.15)Ga(0.85)As were ion implanted with Uranium 238. Uranium-associated emissions were observed in the near infrared region in each semiconductor type except for n-type GaP. The uranium emissions in n-type GaP were too weak to confirm. An annealing temperature dependence study and a sample temperature dependence study were done to associate emissions to specific centers and observe thermal quenching. No effects by the doping of uranium were observed in the band edge emissions except in semi-insulating (SI) InP:U. The optimum annealing temperature for SI-GaAs, SI-InP, and n-type Al(0.15)Ga(0.85)As was 700 C. For n-type GaAs, the optimum annealing temperature was 750 C. The increase in emission intensities with higher annealing temperature suggests a lattice site luminescence center. The similar intensity dependence on sample temperature by each Uranium emission in each semiconductor, implies a single luminescence center. The weakness of uranium emissions shows that uranium-doped semiconductors must be modified to significantly improve the quantum efficiency of the radiation transfer process before they can be seriously considered for use in devices. Keywords: Aluminum gallium arsenides, Theses. (AW)