(CdZnTe,ZnSeTe)/ZnTe复合量子阱中的超快速激子衰减

为了研究低维半导体结构中的激子过程，并进一步实现超快速的激子衰减，设计了一种新型的(CdZnTe，ZnSeTe)／ZnTe复合量子阱结构，并用低压金属有机化学气相沉积方法(LPMOCVD)制备出来。用泵浦-探测方法，采用反射式光路测量了该复合结构中CdZnTe／ZnTe量子阱的激子衰减。单指数衰减拟合给690fs的下降沿时间。     

(CdZnTe,ZnS)/ZnTe复合量子阱的光学特性研究

设计并制备了一种新型的(CdZnTe,ZnS)/ZnTe复合量子阱结构.使CdZnTe量子阱中的激子有可能在短时间内隧穿到ZnS阱层,从而达到提高光双稳器件“关”速度的目的.并通过对发光特性的研究证实在我们设计的结构中横向激子隧穿的存在,从而为进一步研究超高速光开关提供了实验依据.     

ZnCdSe量子阱/CdSe量子点耦合结构中的激子隧穿过程

用室温光致发光谱和飞秒脉冲抽运探测方法对不同垒宽的ZnCdSe量子阱/ZnSe/CdSe 量子点新型耦合结构中激子隧穿过程进行研究，观察到激子从量子阱到量子点的快速隧穿过 程.在ZnSe垒宽为10nm, 15nm, 20nm时，测得激子隧穿时间分别为1.8ps, 4.4ps, 39ps. 关键词： ZnCdSe量子阱 CdSe量子点 激子 隧穿     

ZnCdSe/ZnSe非对称双量子阱中的光学特性研究

用LP-MOCVD技术在GaAs衬底上外延生长了ZnCdSe/ZnSe非对称双量子阱(ADQW)结构。通过ps时间分辨光谱、吸收光谱、发射光谱等的研究得到了如下的结果:在弱激发下,观测到ADQW结构中的激子隧穿现象;在强激发下,在ADQW结构中发现了一个内建电场,它将影响激子隧穿;首次观测到由激子隧穿引起的在一定温度范围内宽阱的发光强度随温度上升而增加的现象;首次观测到该ADQW结构中来自宽阱的光泵受激发射。     

LP-MOCVD生长(ZnCdTe,ZnSeTe)/ZnTe复合量子阱的激子发光研究

用低压金属有机化学气相沉积(LP-MOCVD)的方法在GaAs(100)衬底上生长了(ZnCdTe，ZnSeTe)／ZnTe复合量子阱结构。测量了生长样品的光致发光(PL)谱，得到两个发光峰(记为Il，I2)，分析认为高能侧的峰为Zn0．9Cd0．1Te浅阱峰，而低能侧的峰为ZnSe0．2Te0.8深阱层的发射。对样品进行了变激发强度的PL谱测量，当激发强度增加时，PL谱中两个发光峰的比值(I2／I1)开始时迅速增加，然后缓慢减小。这是由于浅阱中的电子和空穴隧穿入深阱中导致空间电荷的分离，从而在复合量子阱结构中产生了一个内建电场所引起的。     

CdSe/ZnSe复合结构非对称量子阱的发光特性

利用MOCVD技术在GaAs衬底上外延生长了非对称量子阱结构CdSe/ZnSe材料,通过对其稳态变温光谱及变激发功率光谱,研究了其发光特性。稳态光谱表明:在82～141K时,观测到的两个发光峰来源于不同阱层厚度的量子阱激子发光,用对比实验验证了高能侧发光的来源。宽阱发光强度先增加后减小,将其归结为激子隧穿与激子热离化相互竞争的结果。通过Arrhenius拟合,对宽阱激子热激活能进行了计算。82K时变激发功率PL光谱表明:由于激子隧穿的存在,使得窄阱发光峰位不随激发功率变化而变化,宽阱发光峰位随激发功率增加发生了蓝移,并对激子隧穿进行了实验验证。     

基于电子自旋弛豫全光开关中的瞬态特性

设计了基于电子自旋弛豫的透射式全光开关模犁.该光开关具有开关时间短、结构简单,光学非线性强等特点.研究在右旋圆偏振光抽运下 GaAs/AlGaAs半导体多量子阱(MQWs)中以相空间填充(PSF)和库仑屏蔽(CS)为主要因素导致的激子吸收饱和行为,计算与抽运光同向(探测光与抽运光的圆偏振方向相同)和反向(探测光与抽运光的圆偏振方向相反)的圆偏振探测光吸收系数的变化,得到两种圆偏振光差分透射率改变量随延迟时间的变化.实验采用飞秒抽运-探测技术,获得了室温下GaAs/AlGaAs多量子阱同向圆偏振探测光的透射曲线,观察到了明显的饱和吸收现象,与数值模拟的结果相符.     

亚单层InGaAs量子点-量子阱异质结构的时间分辨光致发光谱

测定了亚单层InGaAs/GaAs量子点-量子阱异质结构在5K下的时间分辨光致发光谱.亚单层量 子点的辐射寿命在500 ps 至 800 ps之间，随量子点尺寸的增大而增大，与量子点中激子的 较小的横向限制能以及激子从小量子点向大量子点的隧穿转移有关.光致发光上升时间强烈 依赖于激发强度密度.在弱激发强度密度下，上升时间为 35 ps，纵光学声子发射为主要的 载流子俘获机理.在强激发强度密度下，上升时间随激发强度密度的增加而减小，俄歇过程 为主要的载流子俘获机理.该结果对理解亚单层量子点器件的工作特性非常有用. 关键词： 亚单层 量子点-量子阱 时间分辨光致发光谱     

量子点操控的光子探测和圆偏振光子发射

半导体量子点是研究光子与电子态相互作用的优选固态体系,并在光子探测和发射两个方向上展现出独特的技术机遇.其中基于量子点的共振隧穿结构被认为在单光子探测方面综合性能最佳,但受到光子数识别、工作温度两个关键性能的制约.利用腔模激子态外场耦合效应,有望获得圆偏振态可控的高频单光子发射.本文介绍作者提出的量子点耦合共振隧穿（QD-cRTD）的光子探测机理,利用量子点量子阱复合电子态的隧穿放大,将QD-cRTD光子探测的工作温度由液氦提高至液氮条件,光电响应的增益达到10⁷以上,并具备双光子识别能力;同时,由量子点能级的直接吸收,原型器件获得了近红外的光子响应.在量子点光子发射机理的研究方面,作者实现了量子点激子跃迁和微腔腔模共振耦合的磁场调控,在Purcell效应的作用下增强激子自旋态的自发辐射速率,从而增强量子点中左旋或右旋圆偏振光的发射强度,圆偏度达到90%以上,形成一种光子自旋可控发射的新途径.     

基于InGaAs/InP多量子阱的全光偏振开关的研究

研究了一种基于InGaAs/InP多量子阱的全光偏振开关,讨论了相空间填充(PSF)效应引起的激子饱和以及光学非线性,计算了在抽运光下的阱中载流子布居数随时间的变化,推导出了探测光偏振态的主轴瞬态旋转角.计算结果表明,在100 pJ飞秒脉冲抽运下该全光开关理论旋转角最大可达60°.     

Photoluminescence and exciton resonances over the scattered light in multiphonon spectra of resonant scattering in the CdTe/ZnTe superlattices with narrow quantum wells

Photoluminescence and Raman scattering spectra in CdTe/ZnTe heterostructures and superlattices with narrow quantum wells (4.8–9.2 Å) in a temperature range of 5–300 K have been measured. The temperature dependences of the intensity of exciton luminescence in isolated quantum wells have been studied, and the thermal activation energies associated with the effective barriers for electrons and holes have been determined. In CdTe/ZnTe heterostructures, the binding energies of an exciton with a heavy hole have been determined as functions of the quantum well width. The multiphonon Raman spectra that exhibit distinctive features, such as the weak intensity of nLO phonon lines of ZnTe (n < 8), the absence of their dependence on the number n (n > 2), and the multiple participation in scattering of acoustic LA phonons with large wave vector, have been investigated. The results have been explained based on the concept of the relaxation of hot excitons over the exciton band.     

Exciton polaritons in quantum wells in a transverse magnetic field

Physics of the Solid State - This paper reports on a study of the exciton polariton region in reflection spectra of wide CdTe/CdZnTe quantum wells (with well width exceeding by far the exciton Bohr...     

Exciton Light Emission of CdTe/ZnTe Heterostructures with Double Ultrathin Narrow-Gap Layers

Physics of the Solid State - The exciton luminescence spectra of CdTe/ZnTe heterostructures containing two thin CdTe layers separated by barriers of different thickness were studied. The complex...     

Anomalous phonon wind effect on the lateral exciton migration in ultrathin quantum well CdTe/ZnTe

The effect of nonequilibrium acoustic phonon flux on the photoluminescence of an ultrathin quantum well CdTe/ZnTe upon its quasi-resonant excitation by a He-Ne laser was studied. It is found that the phonon flux generated by an external source affects the quantum well luminescence bandshape even at small lasing power and large (up to 1 cm) distance between the phonon generation zone and the quasi-resonant luminescence excitation zone. It is assumed that the phonon flux stimulates exciton in-plane (lateral) migration in the quantum well through the tunneling between the local potential minima accompanied by induced phonon emission.     

Growth and optical characterization of single quantum well structure of submonolayer ZnS/ZnTe

Single quantum wells of submonolayer ZnS/ZnTe were grown between ZnTe layers using hot wall epitaxy method with fast-movable substrate configuration. As ZnS well widths decrease from 1 to 0.15 monolayer, the photoluminescence peaks shift to higher energies from 2.049 to 2.306 eV, and the photoluminescence intensities increase. As ZnS well width decrease, the PL spectra show the lower-energy tails and consequently the increased PL FWHMs. This is a result of a convolution of two PL peaks from two-dimensional and zero-dimensional quantum islands, supported by a still lived lower-energy peaks of zero-dimensional quantum islands above 50 K. The energy shift in the power dependence of photoluminescence spectra is proportional to the third root of the excitation density. These behaviors can be described by the formation of submonolayer type-II ZnS/ZnTe quantum well structure, and the coexistence of two-dimensional and one-dimensional islands in ZnS layers.     

Manifestation of CdTe quantum dots and interdiffusion in IR reflection spectra of CdTe/ZnTe structures with quantum dots

The IR reflection spectra of structures that consist of alternating layers of CdTe quantum dots and ZnTe barriers and are grown on ZnTe and CdTe/ZnTe buffer layers on GaAs(001) substrates are studied. The spectra are processed using dispersion analysis, and the parameters of the oscillators are determined. In the spectra, quantum dots manifest themselves in the form of a broad band at a frequency close to the frequency of the Fröhlich mode. It is revealed that the spectra contain features associated with the interdiffusion of the CdTe and ZnTe compounds, i.e., bands attributed to the local mode of Zn atoms in the CdTe compound and two gap modes of Cd atoms in the ZnTe compound.     

CdTe/CdZnTe多量子阱激子复合动力学性质的研究

报道了分子束外延制备的高质量CdTe/Cd_0.64Zn_0.36Te多量子阱结构的光学性质,由变温光致发光光谱讨论了随温度升高辐射线展宽和辐射复合效率降低的机理.在变密度激发的皮秒时间分辨光谱中,发现不同激发密度下发光衰减时间不同,并研究了它的机理.在高激发密度下观测到n=2的重空穴激子发光. 关键词：     

Size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots

We investigate size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots (QDs) grown using molecular beam epitaxy and atomic layer epitaxy. Photoluminescence (PL) spectra show that the excitonic peak corresponding to transitions from the ground electronic subband to ground heavy-hole band in CdTe/ZnTe QDs shifts to a lower energy with increasing ZnTe buffer thicknesses. This shift of the PL peak can be attributed to size variation of the CdTe QDs. In particular, carrier dynamics in CdTe QDs grown on various ZnTe buffer layer thicknesses is studied using time-resolved PL measurements. As a result, the decay time of CdTe QDs is shown to increase with increasing ZnTe buffer layer thicknesses due to the reduction of the exciton oscillator strength in the larger QDs.