应变纤锌矿ZnO/Mg_xZn_(1-x)O盘形量子点中的离子施主束缚激子态（英文）

Ionized Donor Bound Exciton States in Strained Wurtzite ZnO/Mg_xZn_(1-x)O Disk-shaped Quantum Dots

在有效质量近似下,计算了盘形量子点中离子施主束缚激子的结合能、光跃迁能、振子强度及辐射寿命.设盘形量子点由有限长的柱形ZnO材料组成,四周被MgxZn1-xO包围,离子施主局域在盘轴.考虑了由于自发极化和压电极化引起的内建电场效应,并在有限深约束势下采用合适的变分波函数进行.计算结果表明,量子盘结构参数(盘高度及垒中Mg组分)和离子施主的位置对离子施主束缚激子的结合能、光跃迁能、振子强度及辐射寿命有强烈的影响.随着盘高度的增加,结合能、光跃迁能和振子强度减小,而辐射寿命增加.对含Mg量较高的盘形量子点,盘高度对结合能、光跃迁能、振子强度及辐射寿命的影响更显著.当施主杂质位于量子点的左界面附近时结合能(光跃迁能)有极大(极小)值,而当施主杂质位于量子点的右界面附近时结合能(光跃迁能)有极小(极大)值.

Within the framework of the effective-mass approximation,the binding energy,optical transition energy,oscillator strength,and radiative lifetime of ionized donor bound exciton（D＋X）in a Quantum Dot（QD）were calculated,assumed that the ionized donor was located at the disk axis,the disk-shaped QD consisted of a finite length cylinder of ZnO material surrounded by MgxZn1-xO.The calculations were performed by using a suitable variational wave function for finite confinement potential at all surfaces,including the strong built-in electric field effect due to the spontaneous and piezoelectric polarizations.Calculated results reveal that the disk structural parameters（height and Mg composition in the barrier）and the donor position have a strong influence on the binding energy,optical transition energy,oscillator strength,and radiative lifetime of（D＋X）complex.As the disk height increases,the binding energy,optical transition energy,and oscillator strength both decrease,whereas the radiative lifetime increases.The influences of disk height on the binding energy,optical transition energy,oscillator strength,and radiative lifetime become more prominent for the QDs with higher Mg composition.The binding energy（the optical transition energy）has a maximum（minimum）when the donor is located in the vicinity of the left interface of the QDs.On the contrary,the binding energy（the optical transition energy）has a minimum（maximum）when the donor is located in the vicinity of the right interface of the QDs.