III族氮化物量子点中类氢施主杂质位置对束缚激子结合能的影响

在有效质量近似下,运用变分方法,考虑内建电场效应和量子点(QD)的三维约束效应的情况下,研究了类氢施主杂质在量子点中的位置对III族氮化物量子点中束缚激子结合能的影响。结果表明:当类氢施主杂质位于量子点中心时,对于InxGa1-xN/GaN量子点,量子点高度和In含量存在临界值,当参数大于临界值时,约束在QD中束缚激子的结合能升高,激子态的稳定性增强,提高了激子的离解温度,使人们能在较高的温度条件下观察到半导体量子点吸收谱中的激子峰。而类氢施主杂质总是使束缚在GaN/A lxGa1-xN量子点中激子的结合能升高,载流子被更强的约束在量子点中。说明对GaN/A lxGa1-xN量子点,杂质使人们能在更高温度下观察到量子点中的激子。类氢施主杂质位于量子点上界面时,束缚激子的结合能最大,系统最稳定;随着施主杂质下移,激子结合能减小,激子的离解温度下降。

Effects of hydrogenic donor impurity position on the binding energy of a bound exciton in Ⅲ-nitrides quantum dots

In this paper,concerning the domino effect of the built-in electric field and the three-dimension confinement,the effects of hydrogenic donor impurity position on the binding energy of a bound exciton in Ⅲ-nitrides quantum dots(QDs) are investigated by means of a variational approach within the framework of effective-mass approximation.The numerical results show that there are critical values on the height of the QDs and In content when there is a hydrogenic donor impurity in the center of In_xGa_(1-x)N/GaN quantum dots.The exciton binding energy and stability of exciton state are increased,when the parameter is larger than the critical value and the exciton dissociation temperature rises.So the exciton absorption peak in the absorotion spectrum of the QDs can be observed in higher temperatures.The exciton binding energy is increased with introducing the impurity into GaN/Al_xGa_(1-x)N quantum dots.The carriers are more strongly confined in the QDs,and the exciton in QDs can be observed in higher temperatures.The influence of the hydrogenic donor impurity position on the exciton binding energy is also investigated in the paper.The results show that the exciton binding energy is the highest and the stability of exciton state is the strongest when the impurity position is on the upper interphase of QDs.As the impurity moves to lower interphase of QDs,the binding energy reduces,and the exciton dissociation temperature drops.