Influence of strain on hydrogenic impurity states in a GaN/AlxGa1?xN quantum dot

Within the effective-mass approximation, we calculated the influence of strain on the binding energy of a hydrogenic donor impurity by a variational approach in a cylindrical wurtzite GaN/Al _x Ga_1−x N strained quantum dot, including the strong builtin electric field effect due to the spontaneous and piezoelectric polarization. The results show that the binding energy of impurity decreases when the strain is considered. Then the built-in electric field becomes bigger with the Al content increasing and the binding energy of hydrogenic donor impurity decreases when the Al content is increasing. For dot height L < 2 nm, the change of the binding energy is very small with the Al content variety. This work has been supported by the National Natural Science Foundation of China (No. 10564003) and the Key Project of the Science and Technology Research of the Educational Ministry of China (No. 208025)     

应变纤锌矿GaN/AlxGa1-xN柱形量子点中的束缚极化子

本文采用有效质量近似,考虑类LO声子,类TO声子以及内建电场的影响,利用变分法研究了应变GaN/AlxGa1-xN柱形量子点中的极化子效应。数值计算表明,极化子效应显著降低了杂质态的结合能。而且,类LO声子对结合能的贡献起主要作用,各向异性的角度和Al组分对结合能的影响则很小。     

Effects of hydrostatic pressure and external electric field on the impurity binding energy in strained GaN/AlxGa1?xN spherical quantum dots

The binding energy and Stark effect energy shifts of a shallow donor impurity state in a strained GaN/AlxGa1-xN spherical finite-potential quantum dot (QD) are calculated using a variational method based on the effective mass approximation. The binding energy is computed as a function of dot size and hydrostatic pressure. The numerical results show that the binding energy of the impurity state increases, attains a maximum value, and then decreases as the QD radius increases for any electric field. Moreover, the binding energy increases with the pressure for any size of dot. The Stark shift of the impurity energy for large dot size is much larger than that for the small dot size, and it is enhanced by the increase of electric field. We compare the binding energy of impurity state with and without strain effects, and the results show that the strain effects enhance the impurity binding energy considerably, especially for the small QD size. We also take the dielectric mismatch into account in our work.     

基于耦合分析的“经济—人口—火灾”系统研究

以《中国统计年鉴》和《中国消防年鉴》2002-2016年我国经济、人口、火灾的相关数据为依据,采用熵值赋权法计算我国经济-人口-火灾系统的权重及综合得分。构建耦合协调度分析模型,研究经济-人口-火灾系统之间是否协调发展。耦合协调度的实证分析表明：我国经济-人口-火灾系统基本上在轻度失调衰退类和中度失调衰退类之间发展,耦合协调度总体上虽然有上升的趋势,但一直处于失调状态。根据分析结果提出了相关建议。     

纤锌矿氮化物半导体束缚极化子及压力效应

考虑到纤锌矿结构的氮化物半导体材料的单轴异性,采用变分法研究了两支异常光学声子LO-like和TO-like对杂质态结合能的影响,即极化子效应.计及电子有效质量,材料介电常数及晶格振动频率随流体静压力的变化,讨论了束缚极化子结合能的压力效应,数值结果表明,极化子效应使杂质态结合能明显降低,极化子效应的主要贡献来自杂质态与LO-like声子的相互作用.压力使得结合能增加,且增强了结合能的各向异性.     

不同处理方式下高压电场对大肠杆菌杀菌效应的比较研究

对大肠杆菌进行高压匀强电场杀菌效应的研究。通过干燥处理和溶液处理的比较实验发现：干燥处理对大肠杆菌灭活效果显著,随着时间的延长、电压的升高,其致死率呈上升趋势;当处理1min时：电压为1kV/cm存活率是对照的6倍以上,电压为2kV/cm,存活率是对照的约一半左右,之后随电压的升高,存活率与对照相比在20%上下波动;当处理10min时：电压为1kV/cm存活率是对照的49%,电压达3kV/cm及以上时,存活率为3%及以下。溶液处理下对大肠杆菌的灭活效果较差,存活率总的变化趋势呈振荡型。一定强度的场强可以促进大肠杆菌的萌发,使存活率提高。结果表明,相对溶液处理,干燥处理的杀菌效果显著,可望开发应用于干燥物料的消毒杀菌。     

Bound polaron in a strained wurtzite GaN/Al_xGa_(1-x)N cylindrical quantum dot

Within the effective-mass approximation,a variational method is adopted to investigate the polaron effect in a strained GaN/Al_xGa_1-xN cylindrical quantum dot.The electron couples with both branches of longitudinal optical-like（LO-like）and transverse optical-like（TO-like）phonons and the built-in electric field are taken into account.The numerical results show that the binding energy of the bound polaron is reduced obviously by the polaron effect on the impurity states.Furthermore,the contribution of LO-like phonons to the binding energy is dominant,and the anisotropic angle and Al content influence on the binding energy are small.     

Influence of strain on hydrogenic impurity states in a GaN/ Al_xGa_(1-x)N quantum dot

Within the effective-mass approximation, we calculated the influence of strain on the binding energy of a hydrogenic donor impurity by a variational approach in a cylindrical wurtzite GaN/AlxGa1-xN strained quantum dot, including the strong built- in electric field effect due to the spontaneous and piezoelectric polarization. The results show that the binding energy of impurity decreases when the strain is considered. Then the built-in electric field becomes bigger with the Al content increasing and the bin...     

纤锌矿氮化物半导体束缚极化子及压力效应

考虑到纤锌矿结构的氮化物半导体材料的单轴异性,采用变分法研究了两支异常光学声子LO-like和TO-like对杂质态结合能的影响,即极化子效应.计及电子有效质量,材料介电常数及晶格振动频率随流体静压力的变化,讨论了束缚极化子结合能的压力效应,数值结果表明,极化子效应使杂质态结合能明显降低,极化子效应的主要贡献来自杂质态与LO-like声子的相互作用.压力使得结合能增加,且增强了结合能的各向异性.     

Influence of surface optical phonon on the electronic surface states in wurtzite group-Ⅲ nitride ternary mixed crystals

An intermediate-coupling variational method is presented to investigate the surface electron states in wurtzite A_xB_1-xN(A, B=Al, Ga and In) ternary mixed crystals(TMCs). Corresponding effective Hamiltonian are derived by considering the surface-optical-phonon(SO-phonon) influence and anisotropic structural effect. The surface-state energies of electron, the coupling constants and the average penetrating depths of the electronic surface-state wave functions have been numerical computed as a function of the composition x and the surface potential V₀ for the wurtzite Al_xGa_1-xN, Al_xIn_1-xN and In_xGa_1-xN, respectively. The results show that the surface-state levels of electron are reduced with the increasing of the composition x in wurtzite A_xB_1-xN. It is also found that the electron-surface-optical-phonon(e-SO-p) coupling lowers the surface-state energies of electron and the shifts of the electronic surface-state energy level in the wurtzite Al_xGa_1-xN and Al_xIn_1-xN increase with the increasing of the composition x. However, in the wurtzite In_xGa_1-xN, the case is contrary. The influence of the e-SO-p interaction on the surface electron states can not be neglected in wurtzite A_xB_1-xN.