Effects of Hydrogenic Impurity on Bound Exciton States in In_xGa_(1-x)N/GaN and GaN/Al_xGa_(1-x)N 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-xN 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 QDs.