中文摘要：

以Bi和Cu掺杂为例,通过基于密度泛函理论的电子结构的计算,分析了SrTiO3体系中形成级联能级的可能性.结果表明,Bi掺杂和Cu掺杂都可以在SrTiO3的禁带中引入杂质能带,Bi和Cu的共同掺杂可引入两条杂质能带.通过在两条杂质能带之间级联激发,价带顶的电子可以受激跃迁到导带底.采用无辐射跃迁的简单模型,分析指出电子通过级联激发从价带顶受激跃迁到导带底的概率远远高于直接从价带顶跃迁到导带底的概率.这种级联激发可以有效提高导带中的载流子浓度.

英文摘要：

The possibility of forming cascading energy levels in SrTiO_3 by doping Bi and Cu as an example is analyzed by using the density-functional-theory based first principles calculations of the electronic structure.The results show that both Bi doping and Cu doping can introduce a defect level in the forbidden band,and Co-doping of Bi and Cu can introduce two defect levels in the forbidden band.Electrons at the top of valence band can transit to the bottom of conduction band through a cascade transition process. Using the nonradiative transition model, we point out that the probability of electronic transition from the valence band to the conduction band through a cascade transition is much higher than that of direct transition from the valence band to the conduction band. The cascade transitions can effectively increase the carrier concentration in the conduction band.