纤锌矿GaN/AlxGa1-xN量子阱中自由极化子能级

采用Lee-Low-Pines (LLP)变分法研究了纤锌矿GaN/Al0.3Ga0.7N量子阱中自由极化子能量和电子-声子相互作用对自由极化子能量的影响.理论计算中考虑了量子阱中定域声子模(Confined phonon modes)和半空间声子模(Half-space phonon modes)的影响以及电子有效质...     

纤锌矿GaN/AlxGa1-xN量子阱中激子能量

考虑了纤锌矿GaN/Al<,x>Ga<,1-x>N量子阱(QW)材料中空穴带质量和光学声子模的各向异性以及声子频率随波矢变化的效应,采用改进的LLP变分法计算了纤锌矿氮化物QW中激子的基态能量和结合能.给出了激子的基态能量和结合能随着QW宽度和Al组分变化的函数关系,并对闪锌矿和纤锌矿GaN/Al<0.3>Ga<,0....     

非对称应变纤锌矿AlxGa1-xN/GaN/AlyGa1-yN量子阱中浅杂质态的结合能

本文采用变分法数值计算应变纤锌矿AlxGa1−xN/GaN/AlyGa1−yN量子阱中类氢杂质的基态结合能. 计及由自发极化和压电极化引起的内建电场, 讨论阱宽、杂质位置以及左右垒中Al组分对结合能的影响. 结果表明, 尤其在非对称量子阱即势垒宽度或（和）高度不一样的情形下, 杂质位置和垒高对结合能随阱宽变化关系的影响比垒宽更为明显. 对称或非对称结构中, 结合能随杂质位置的变化形如电子基态波函数的空间分布. 此外, 左垒中Al组分对结合能的影响较右垒更甚.     

Cd1-xMnxTe/CdTe抛物量子阱内激子结合能的研究

在有效质量近似下采用变分法计算了Cd1-xMnxTe/CdTe抛物量子阱内不同Mn组分下激子的结合能,给出了结合能在不同Mn组分下随阱宽、垒宽、外加电场的变化情况。 结果表明:激子结合能是阱宽的一个非单调函数，随阱宽的变化呈现先增加后减小的趋势，而且随着Mn组分增大, 激子结合能达到最大值的阱宽相应变小, 这与材料的带隙改变有关;激子结合能随垒宽逐渐增大然后趋于稳定值，这与波函数向垒中的渗透有关；在一定范围内电场对激子结合能的影响很小,而且Mn组分越大对激子结合能影响越小，但电场强度较大时会破坏激子效应。计算结果可以对基于半导体抛物形量子阱发光器件设计制作提供一些理论依据。     

Binding energies of shallow impurities in asymmetric strained wurtzite AlxGa1-xN/ GaN/Aly Ga1-yN quantum wells

The ground state binding energies of hydrogenic impurities in strained wurtzite AlxGa1-xN/GaN/AlyGa1-y>N quantum wells are calculated numerically by a variational method. The de-pendence of the binding energy on well width, impurity location and Al concentrations of the left and right barriers is discussed, including the effect of the built-in electric field induced by spontaneous and piezoelectric polarizations. The results show that the change in binding energy with well width is more sensitive to the impurity position and barrier heights than the barrier widths, especially in asymmetric well structures where the barrier widths and/or barrier heights differ. The binding energy as a function of the impurity position in symmetric and asymmetric structures behaves like a map of the spatial distribution of the ground state wave function of the electron. It is also found that the influence on the binding energy from the Al concentration of the left barrier is more obvious than that of the right barrier.     

在磁场作用下氮化物抛物量子阱中杂质态能量

采用变分法研究了在外磁场作用下GaN／AlxGa1-xN无限抛物量子阱（PQW）中类氢杂质态能级,给出不同磁场下杂质态基态能、结合能随阱宽的变化关系以及能量随磁场强度变化的函数关系。数值结果表明：外磁场对类氢杂质能量和结合能均有明显的影响,杂质态能量随磁场的增强而显著增大,并且随阱宽的增大而增大;GaN／Al0.3Ga0.7 N PQW对杂质态的束缚程度比GaAs／Al0.3Ga0.7As PQW强。     

AlxGa1−xN/GaN multi-quantum-well ultraviolet detector based on p-i-n heterostructures

We report on characterization of a set of AlGaN/GaN multiple-quantum-well (MQW) photodetectors. The model structure used in the calculation is the p-i-n heterojunction with 20 AlGaN/GaN MQW structures in i-region. The MQW structures have 2 nm GaN quantum well width and 15 nm Al_xGa_1−xN barrier width. The cutoff wavelength of the MQW photodetectors can be tuned by adjusting the well width and barrier height. Including the polarization field effects, on increasing Al mole fraction, the transition energy decreases, the total noise increases, and the responsivity has a red shift, and so the detectivity decreases and has a red shift.     

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.     

GaAs/Ga1-xAlxAs量子阱线中类氢杂质的束缚能和光致电离截面

通过在波函数中考虑量子线的限制方向和非限制方向的相关性,计算了GaAs/Ga1-xAlxAs量子阱线中类氢杂质的束缚能和光致电离截面.结果表明光致电离截面的大小受量子线尺寸的影响,并且对于相同尺寸的量子线,有限深势阱中杂质态的光致电离截面要比无限深势阱中的大.与他人的结果比较发现,所选波函数改进了体系的束缚能,并使光致电离截面减小,这使得结果更为合理.     

GaAs/Ga_(1-x)Al_xAs量子阱线中类氢杂质的束缚能和光致电离截面

通过在波函数中考虑量子线的限制方向和非限制方向的相关性,计算了Ga As/ Ga1 - x Alx As量子阱线中类氢杂质的束缚能和光致电离截面.结果表明光致电离截面的大小受量子线尺寸的影响,并且对于相同尺寸的量子线,有限深势阱中杂质态的光致电离截面要比无限深势阱中的大.与他人的结果比较发现,所选波函数改进了体系的束缚能,并使光致电离截面减小,这使得结果更为合理     

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。     

外加电场对GaN/AlxGa1-xN双量子阱中性施主束缚能的影响

在有效质量包络函数理论下,利用变分法计算了未加电场以及加入电场后 双量子阱中施主杂质各种情况下的束缚能,讨论了双量子阱中间势垒高度、施主杂质位置对杂质束缚能的影响。给出了加入电场后施主位置不同时的束缚能和波函数,以及量子阱宽度不同时的束缚能,并且计算了未加电场和加入电场后中间势垒高度变化以及宽度不同时的束缚能。当双量子阱中间垒宽一定时,束缚能随着阱宽的变化会出现一个峰值。在阱宽一定时,随着中间垒宽度的增加,束缚能逐渐减小,并在垒宽增加到一定宽度时双量子阱情况与单量子阱情况相似,束缚能不再明显变化。计算结果对设计和研究 量子阱发光和探测器件有一定的参考价值。     

Al_xGa_(1-x)N/GaN异质结构中二维电子气的自旋性质

Ⅲ族氮化物材料有很长的电子自旋弛豫时间以及很高的居里温度,成为近年来半导体自旋电子学研究的重要材料体系之一。介绍了目前两种最主要的研究AlxGa1-xN/GaN异质结构中二维电子气(2DEG)自旋性质的物理效应:磁电阻的舒伯尼科夫-德哈斯拍频振荡和弱反局域效应,回顾了AlxGa1-xN/GaN异质结构中2DEG自旋性质的研究进展。AlxGa1-xN/GaN异质结构材料中有很强的极化电场,诱导产生很高浓度的2DEG,能够产生相当大能量的自旋分裂,并且这种自旋分裂可以被栅压所调控,因此在自旋场效应晶体管方面有很好的应用前景。然而要实现GaN基自旋电子学器件的应用,GaN中自旋注入效率是目前所面临的问题。     

XPS Investigation on Surface and Interface Electronic States of Alq3／ITO

The surface and interface electronic states of tris-(8-hydroxyquinoline)aluminum(Alq3)/indium-tin oxid(ITO)were measured and analyzed by X-ray photoelectron spectroscopy(XPS).The results indicated that, in Alq3 molecule,the binding energy(Eb)of Al atoms is 70.7eV and 75.1eV,corresponding to Al(O)and Al(Ⅲ）,respectively;The binding energy of C is 285.8eV,286.3eV,and 286.8eV,corresponding to C of C-C group,C-O,and C-N bond,respectively,N is the main peak locating at 401.0eV, corresponding to Natom of C-N=C.Oatoms mainly bond o H atom,with the binding energy of 533.2 eV.As the sputtering time of Ar^ ion bearn increases,Al2p,C1s,N1s,O1s,Ind3d5/2 and Sn3d5/2 peaks slightly shift towards lower binding energy,and Al2p,C1s and N1s peaks get weaker,which contributed to diffusing the oxygen,indium and tin in ITO into Alq3 layr.     

GaxIn1-xAsyP1-y-InPtensile-strained quantum wells for 1.3-μm low-threshold lasers

Ga_xIn_1-xAs_yP_1-y-InP tensile-strained multiple quantum wells (MQWs) grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) are studied for the application to 1.3-μm lasers. High-resolution X-ray diffraction curves show good agreement with theoretical simulation. Clear energy separation of light hole and heavy hole bands is observed in the room temperature photoluminescence measurement. Threshold characteristics of -1.15% tensile-strained MQW lasers with graded index separate confinement heterostructure (GRINSCH) are investigated. The minimum threshold current density per well (J_th/N_w) for infinite cavity length obtained is 100 A/cm² for the device with a well number of 3. Tensile strain dependence of J_th/N _w for an infinite cavity is also clarified     

在外电场作用下有限抛物量子阱中类氢杂质态结合能

采用变分方法研究GaAs/AlxGa1-xAs有限抛物量子阱中类氢杂质态能量和结合能随外电场和阱宽的变化关系.在计算中考虑了电子有效带质量和介电常数随空间坐标(或合金组分)的变化因素.结果表明,外电场对类氢杂质态能量和结合能均有明显的影响,并且这些影响随着阱宽的增大而增大.电子有效带质量和介电常数随空间坐标的变化效应使得类氢杂质态基态能量减小,结合能增大,此效应随着阱宽的增大明显变小.     

Modification of the Intermediate Binding Energies on Ni/Ni3N Heterostructure for Enhanced Alkaline Hydrogen Oxidation Reaction

Developing highly efficient and stable non-precious metal-based electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is essential for the commercialization of alkaline exchange membrane fuel cells but remains a big challenge. Here, a simple strategy for constructing the Ni/Ni₃N heterostructure electrocatalyst with remarkable catalytic performance toward HOR under alkaline electrolyte is reported. Density functional theory calculations and experimental results reveal that the inter-regulated d-band center of interfacial Ni and Ni₃N derived from electron transfer from Ni to Ni₃N across the interface can lead to the weakened hydrogen binding energy of Ni and strengthened hydroxyl binding energy of Ni₃N, which, together with the decreased formation energy of water species, contributes to the outstanding HOR performance.     

纤锌矿InxGa1-xN/GaN量子阱中的界面声子模

采用赝原胞模型计算讨论纤锌矿InxGa1-xN混晶性质;基于宏观介电连续模型的传递矩阵方法研究任意层纤锌矿量子阱中的界面声子,得出任意层纤锌矿量子阱中的界面声子的本征模解和单量子阱的色散关系,并对InxGa1-xN/GaN单量子阱界面声子的色散关系进行了数值计算和讨论。结果表明,纤锌矿InxGa1-xN混晶中的E1声子和A1声子都表现为单模行为;在对称非应变单量子阱GaN/InxGa1-xN/GaN中,界面声子频率随x的变化呈线性关系。     

Modeling of optical gain in InGaN-AlGaN andInxGa1-xN-InyGa1-yNquantum-well lasers

This paper presents computations of the optical gain in In_x Ga_1-xN-In_yGa_1-yN and InGaN-AlGaN quantum-well lasers involving the contributions of excitons as well as free carriers transitions. The behavior of optical gain in GaN based quantum wells due to excitonic transitions is quite similar to that of ZnCdSe-ZnSSe system, as the magnitude of the exciton binding energies (~30 meV) is comparable. The model compares the exciton emission energy with the experimental data reported on In_0.22Ga_0.78N-In_0.06Ga_0.94N multiple quantum wells as well as in GaN layers (cubic grown on 3C SiC), including the effect of strain induced band gap changes. The optical gain is also computed as a function of the injection current density for the InGaN-AlGaN multiple quantum-well lasers. The model evaluates the feasibility of obtaining GaN based blue and ultraviolet lasers. It is shown that the excitonic transitions reduce the threshold current density which is adversely affected by the presence of dislocations and other defects     

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...