类氢杂质对In_xGa_（1-x）N/GaN和GaN/Al_xGa_（1-x）N量子点中束缚激子态的影响

在考虑内建电场效应和量子点（QD）的三维约束效应的情况下,运用变分方法研究了类氢施主杂质的位置对Ⅲ族氮化物量子点中束缚激子态的影响.结果表明：当类氢施主杂质位于量子点中心,InxGa1-xN/GaN量子点的高度和In含量大于临界值时,约束在QD中激子的基态能降低,激子态的稳定性增强,在较高的温度下观察到半导体量子点吸收谱中的激子峰,发光波长增大.而类氢施主杂质总是使束缚在GaN/AlxGa1-xN量子点中激子的基态能降低,杂质可能使在更高温度下观察到GaN/AlxGa1-xN量子点中的激子,发光波长增大.研究发现类氢施主杂质位于量子点上界面时,激子的基态能最小,系统最稳定;随着施主杂质下移,激子基态能增加,激子的解离温度下降,发光波长减小.

Effects of Hydrogenic Impurity on Bound Exciton States in In_xGa1-xN/GaN and GaN/AlxGa1-xN Quantum Dots

Concerning the domino effect of the built-in electric field and the three-dimension confinement,the effects of hydrogenic donor impurity position on bound exction states 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 InxGa1-xN/GaN quantum dots. The exciton ground-state energy is reduced, and the emission wavelength and stability of exciton state are increased when the parameter is larger than the critical value, and the impurity is easily introduced into the QDs. The exciton ground-state energy is reduced, and the emission wavelength increases with introducing the impurity into GaN/AlxGa1-x N quantum dots, so it is easy to introduce the impurity into GaN/AlxGa1-xN QDs. The influence of the hydrogenic donor impurity position on the exciton states is also investigated. The results show that the exciton ground-state energy is the lowest, 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 ground-state energy increases, and the emission wavelength is reduced. It is proved that hydrogenic donor impurity easily exists in the upper interphase of the ODs.