压力及屏蔽对无限深量子阱中施主结合能的影响

对GaAs/Al_xGa_1-xAs和GaN/Al_xGa_1-xN无限深量子阱系统,考虑压力及屏蔽效应,利用变分方法数值计算这两种系统中的杂质态结合能。给出了结合能随阱宽和压力的变化关系,同时讨论了有无屏蔽时的区别。结果表明,结合能随压力增大而增大,随阱宽增大而减小;屏蔽效应随着压力的增加而增加,并且显著降低了杂质态的结合能。     

磁场下半导体GaAs/AlxGa1-xAs异质结中的杂质态

对异质结势采用三角势近似,考虑屏蔽效应,用变分法讨论磁场下半导体异质结系统中的施主杂质态,数值计算了GaAs/AlxGa_1-xAs单异质结系统中杂质态结合能随磁场的变化关系。结果表明,由于外界磁场使界面附近束缚于正施主杂质的单电子波函数的定域性增强,从而对杂质态的结合能有明显的影响,结合能随磁感应强度的增强而显著增大。还计算了杂质位置、电子面密度产生的导带弯曲以及屏蔽效应诸因素对结合能的影响。结果显示,结合能对电子面密度和杂质位置的变化十分敏感,屏蔽则使得有效库仑吸引作用减弱而导致结合能明显下降。     

应变纤锌矿GaN/AlxGa1-xN柱形量子点中类氢施主杂质态结合能的压力效应

考虑应变,在有效质量、有限高势垒近似下,变分研究了纤锌矿GaN/AlxGa1-xN柱形量子点中类氢施主杂质态结合能随流体静压力、杂质位置及量子点结构参数(量子点高度、半径、Al含量)的变化关系．结果表明,类氢施主杂质态结合能随流体静压力增大而增大,且在量子点尺寸较小时,流体静压力对杂质态结合能的影响更为显著．受流体静压力的影响,杂质态结合能随量子点高度、半径的增加而单调减少,且变化趋势加剧;随Al含量增加而增大的趋势变缓．无论是否施加流体静压力,随着类氢施主杂质从量子点左界面沿材料生长方向移至右界面,杂质态结合能在量子点的右半部分存在一极大值．流体静压力使得极大值点向量子点中心偏移．     

应变纤锌矿GaN/AlxGa1-xN柱形量子点中类氢施主杂质态结合能的压力效应

考虑应变,在有效质量、有限高势垒近似下,变分研究了纤锌矿GaN/AlxGa1 -xN柱形量子点中类氢施主杂质态结合能随流体静压力、杂质位置及量子点结构参数(量子点高度、半径、Al含量)的变化关系.结果表明,类氢施主杂质态结合能随流体静压力增大而增大,且在量子点尺寸较小时,流体静压力对杂质态结合能的影响更为显著.受流体静压力的影响,杂质态结合能随量子点高度、半径的增加而单调减少,且变化趋势加剧;随Al含量增加而增大的趋势变缓.无论是否施加流体静压力,随着类氢施主杂质从量子点左界面沿材料生长方向移至右界面,杂质态结合能在量子点的右半部分存在一极大值.流体静压力使得极大值点向量子点中心偏移.     

纤锌矿In_(0.19)Ga_(0.81)N/GaN量子阱中光学声子和内建电场对束缚极化子结合能的影响

用改进的Lee-Low-Pines变分方法研究纤锌矿In0.19Ga0.81N/GaN量子阱结构中束缚极化子能量和结合能等问题,给出基态结合能、不同支长波光学声子对能量和结合能的贡献随阱宽和杂质中心位置变化的数值结果.在数值计算中包括了该体系中声子频率的各向异性和内建电场对能量和结合能的影响、以及电子和杂质中心与长波光学声子的相互作用.研究结果表明,In0.19Ga0.81N/GaN量子阱材料中光学声子和内建电场对束缚极化子能量和结合能的贡献很大,它们都引起能量和结合能降低.结合能随着阱宽的增大而单调减小,窄阱中减小的速度快,而宽阱中减小的速度慢.不同支声子对能量和结合能的贡献随着阱宽的变化规律不同.没有内建电场时,窄阱中,定域声子贡献小于界面和半空间声子贡献,而宽阱中,定域声子贡献大于界面和半空间声子贡献.有内建电场时,定域声子贡献变小,而界面和半空间声子贡献变大,声子总贡献也有明显变化.在In0.19Ga0.81N/GaN量子阱中,光学声子对束缚极化子能量和结合能的贡献比GaAs/Al0.19Ga0.81As量子阱中的相应贡献(约3.2—1.8和1.6—0.3 meV)约大一个数量级.阱宽(d=8 nm)不变时,在In0.19Ga0.81N/GaN量子阱中结合能随着杂质中心位置Z0的变大而减小,并减小的速度变快.随着Z0的增大,界面和半空间光学声子对结合能的贡献缓慢减小,而定域光学声子的贡献缓慢增大.     

应变纤锌矿GaN/AlχGa1-χN柱形量子点中类氢施主杂质态结合能的压力效应

考虑应变,在有效质量、有限高势垒近似下,变分研究了纤锌矿GaN/Al_xGa_1-xN柱形量子点中类氢施主杂质态结合能随流体静压力、杂质位置及量子点结构参数（量子点高度、半径、Al含量）的变化关系.结果表明,类氢施主杂质态结合能随流体静压力增大而增大,且在量子点尺寸较小时,流体静压力对杂质态结合能的影响更为显著.受流体静压力的影响,杂质态结合能随量子点高度、半径的增加而单调减少,且变化趋势加剧;随A1含量增加而增大的趋势变缓.无论是否施加流体静压力,随着类氢施主杂质从量子点左界面沿材料生长方向移至右界面,杂质态结合能在量子点的右半部分存在一极大值.流体静压力使得极大值点向量子点中心偏移.     

压力下应变异质结中施主杂质态的Stark效应

对应变GaN/Al_xGa_1-xN异质结系统,考虑理想界面突变势垒,引入简化相干势近似,采用变分法讨论了流体静压力下外界电场对束缚于界面附近的浅杂质态结合能的影响.对GaN为衬底的闪锌矿应变异质结,分别计算了(001)和(111)取向时杂质态的结合能随压力、杂质位置、电场强度以及组分的变化关系.结果表明,杂质态结合能随流体静压力呈近线性变化.电场对杂质态的Stark效应则随杂质位置不同而呈现谱线蓝、红移动.此外,还讨论了在不同压力情况下,Al组分对杂质结合能的影响.当杂质处于GaN材料中且距界面较远时,Al组分的增加使电子的二维特性增强,从而使结合能增大,且压力加剧增幅的增加;当杂质处于Al_xGa_1-xN材料中,Al组分的增加削弱了杂质与电子间的库仑相互作用,故而结合能降低. 关键词： xGa_1-xN异质结')" href="#">GaN/Al_xGa_1-xN异质结 杂质态 压力 Stark效应     

外电场下极性量子阱中杂质态结合能

我们用变分方法研究了外电场下量子阱中的杂质态结合能,计算中既考虑了电子同体纵光学声子和界面光学声子的相互作用又考虑了杂质中心同体纵光学声子和界面光学声子的相互作用。我们以GaAs/Al_0.3Ga_0.7As量子阱为例,讨论了结合能随杂质位置、阱宽和电场强度的变化规律。得到了电子-声子相互作用对杂质态结合能和斯塔克效应的修正是相当明显的。     

氮化物抛物量子阱中类氢杂质态能量

采用变分方法研究氮化物抛物量子阱(GaN/Al_xGa_1-xN)材料中类氢杂质态的能级,给出基态能量、第一激发态能量、结合能和跃迁能量等物理量随抛物量子阱宽度变化的函数关系.研究结果表明,基态能量、第一激发态能量、基态结合能和1s→2p±跃迁能量随着阱宽L的增大而减小,最后接近于GaN中3D值.GaN/Al_0.3Ga_0.7N抛物量子阱对杂质态的束缚程度比GaAs/Al_0.3Ga_0.7As抛物量子阱强,因此,在GaN/Al_0.3-Ga_0.7N抛物量子阱中束缚于杂质中心处的电子比在GaAs/Al_0.3Ga_0.7As抛物量子阱中束缚于杂质中心处的电子稳定.     

纤锌矿InGaN staggered量子阱中的激子态和光学性质

本文将基于有效质量近似下的变分法,理论研究了纤锌矿InGaN/GaN staggered 量子阱中的激子态和光学性质。数值结果显示了InGaN量子阱中的量子尺寸和staggered受限垒对束缚于量子阱中的激子态和光学性质有着明显地影响。当阱宽增加时,量子受限效应减弱,激子结合能降低, 带间发光波长增加。另一方面,当量子阱中staggered受限势增加时,量子受限效应增强,激子结合能升高,带间发光波长降低。本文的理论结果证明了可以通过调节staggered垒高和量子尺寸来调控纤锌矿InGaN staggered 量子阱中的激子态和光学性质。     

Comparison of external electric and magnetic fields effect on binding energy of hydrogenic donor impurity in different shaped quantum wells

The effects of external electric and magnetic fields on the ground state binding energy of hydrogenic donor impurity are compared in square, V-shaped, and parabolic quantum wells. With the effective-mass envelope-function approximation theory, the ground state binding energies of hydrogenic donor impurity in InGaAsP/InP QWs are calculated through the plane wave basis method. The results indicate that as the quantum well width increases, the binding energy changes most fast in SQW. When the well width is fixed, the binding energy is the largest in VQW for the donor impurity located near the center of QWs. For the smaller and larger well width, the electric field effect on binding energy is the most significant in VQW and SQW, respectively. The magnetic field effect on binding energy is the most significant in VQW. The combined effects of electric and magnetic fields on the binding energy of hydrogenic donor impurity are qualitative consistent in different shaped QWs.     

Electronic and Shallow Impurity States in Semiconductor Heterostructures Under an Applied Electric Field

With the use of variational method to solve the effective mass equation, we have studied the electronic and shallow impurity states in semiconductor heterostructures under an applied electric field. The electron energy levels are calculated exactly and the impurity binding energies are calculated with the variational approach. It is found that the behaviors of electronic and shallow impurity states in heterostructures under an applied electric field are analogous to that of quantum wells. Our results show that with the increasing strength of electric field, the electron confinement energies increase, and the impurity binding energy increases also when the impurity is on the surface, while the impurity binding energy increases at first, to a peak value, then decreases to a value which is related to the impurity position when the impurity is away from the surface. In the absence of electric field, the result tends to the Levine＇s ground state energy （-1/4 effective Rydberg） when the impurity is on the surface, and the ground impurity binding energy tends to that in the bulk when the impurity is far away from the surface. The dependence of the impurity binding energy on the impurity position for different electric field is also discussed.     

Screening influence on the Stark effect of impurity states in strained wurtzite GaN/AlxGa1-xN heterojunctions under pressure

The screening effect of the random-phase-approximation on the states of shallow donor impurities in free strained wurtzite GaN/Al x Ga 1 x N heterojunctions under hydrostatic pressure and an external electric field is investigated by using a variational method and a simplified coherent potential approximation.The variations of Stark energy shift with electric field,impurity position,Al component and areal electron density are discussed.Our results show that the screening dramatically reduces both the blue and red shifts as well as the binding energies of impurity states.For a given impurity position,the change in binding energy is more sensitive to the increase in hydrostatic pressure in the presence of the screening effect than that in the absence of the screening effect.The weakening of the blue and red shifts,induced by the screening effect,strengthens gradually with the increase of electric field.Furthermore,the screening effect weakens the mixture crystal effect,thereby influencing the Stark effect.The screening effect strengthens the influence of energy band bending on binding energy due to the areal electron density.     

Diamagnetic susceptibility of a laser dressed donor in a quantum well

The binding energy of laser dressed donor impurity is calculated under the influence of a magnetic field in a quantum well. The binding energy of the ground state of a donor is investigated, within the single band effective mass approximation, variationally for different concentrations at the well centre. The effect of laser and magnetic fields on diamagnetic susceptibility of the hydrogenic donor is reported. The Landau energy levels of electrons in the quantum well as a function of magnetic field are reported. The results show that the diamagnetic susceptibility (i) decreases drastically as intensity of the laser field increases (ii) increases with the magnetic field strength (iii) decreases as the Al-concentration decreases and (iv) a variation of increase in binding energy is observed when non-parabolicity is included and this effect is predominant for narrow wells. Our results are in good agreement with previous investigations for other heterostructures in the presence of laser intensity.     

温度与外磁场对Si均匀掺杂的GaAs量子阱电子态结构的影响

本文在有效质量近似下,通过自洽地求解薛定鄂方程及泊松方程计算了在温度T=273 K,磁感应强度B=25 T,Si均匀掺杂的GaAs/AlGaAs量子阱系统的电子态结构.研究了温度与外磁场对子带能量,本征包络函数,自洽势,电子密度分布,及费米能量的影响.发现在给定磁感应强度B=fi0下,随温度升高子带能量单调增加,费米能量单调递减,自洽势的势阱变深变陡,电子密度分布变宽,峰值降低;在给定温度下,随磁感应强度的增加子带能量及费米能量单调递增,自洽势阱变浅变宽,电子密度分布变窄,峰值升高.     

Pressure influence on the Stark effect of impurity states in a strained wurtzite GaN/AlxGa1-xN heterojunction

A variational method is adopted to investigate the properties of shallow impurity states near the interface in a free strained wurtzite GaN/AlxGa1-xN heterojunction under hydrostatic pressure and external electric field by using a simplified coherent potential approximation. Considering the biaxial strain due to lattice mismatch or epitaxial growth and the uniaxial strains effects, we investigated the Stark energy shift led by an external electric field for impurity states as functions of pressure as well as the impurity position, Al component and areal electron density. The numerical result shows that the binding energy near linearly increases with pressure from 0 to 10 GPa. It is also found that the binding energy as a function of the electric field perpendicular to the interface shows an un-linear red shift or a blue shift for different impurity positions. The effect of increasing x on blue shift is more significant than that on the red shift for the impurity in the channel near the interface. The pressure influence on the Stark shift is more obvious with increase of electric field and the distance between an impurity and the interface. The increase of pressure decreases the blue shift but increases the red shift.