压电调制反射光谱研究GaAs/Al0.29Ga0.71 As单量子阱

报道了压电调制反射测量系统的建立,应用该系统获得了势阱宽度分别为5nm和25nm的两个GaAs/Al0.29Ga0.71As单量子阱的压电调制反射谱.从图谱中可以看出,在室温下能够较容易地分辨出和轻、重空穴相关联的子带跃迁.在阱宽25nm的样品中还观察到了自旋-轨道跃迁.利用有效质量理论近似计算,对量子阱样品的图谱结构进行了指认,发现实验值和计算值能够较好地符合.     

应力导致InAs/In0.15Ga0.85As量子点结构中In0.15Ga0.85As阱层的合金分解效应研究

利用固源分子束外延技术，在In_0.15Ga_0.85As/GaAs量子阱生长了两个InAs/In_0.15Ga_0.85As量子点(DWELL)样品.通过改变其中一个InAs DWELL样品中的In_0.15Ga_0.85As阱层的厚度和生长温度，获得了量子点尺寸增大而且尺寸分布更均匀的结果.结合光致发光光谱(PL)和压电调制光谱(PzR)实验结果，发现该样品量子点的光学性质也同时得到 关键词： 合金分解效应 0.15Ga_0.85As量子点')" href="#">InAs/In_0.15Ga_0.85As量子点 光致发光光谱 压电调制光谱     

GaAs/Al0.23Ga0.77As双量子阱的带边不连续性和阱间耦合

本文报道在300和77K对一组具有不同垒宽L_b0.23Ga_0.77As双量子阱样品的光调制反射谱(PR)的研究结果。除观察到11H,11L和22H等容许跃迁外,同时还识别一个从Al_0.23Ga_0.77As价带顶至量子阱第一电子束缚能级的跃迁,另一个从量子阱第一轻空穴束缚能级至Al_0.23Ga_0.77As导带底的跃迁。利用这些跃迁确定导带边不连续性为0.63。对L_{b关键词：}     

Al/GaAs表面量子阱界面层的原位光调制反射光谱研究

用分子束外延（MBE）方法在GaAs表面量子阱上外延生长不同厚度的Al层，以超高真空下的原位光调制光谱（PR）作为测量手段，研究Al扩散形成的表面势垒层对于GaAs表面量子阱中带间跃迁峰位和峰形的影响.根据跃迁峰的变化，采用有效质量近似理论计算出了Al和GaAs 的互扩散长度为0.5nm，这是半导体工艺中的一个重要常数. 关键词： Al GaAs 原位光调制反射光谱（PR） 分子束外延（MBE）     

InAs/GaAs表面量子点的压电调制反射光谱研究

运用压电调制反射光谱(PzR)方法测量了在以GaAs(311)B为衬底的In_0.35Ga_0.65As模板上生长的InAs表面量子点结构的反射谱.在77K温度下，观察到了来自样品各个组成结构(包括表面量子点本身、被覆盖层覆盖的量子点、In_0.35Ga_0.65As模板以及GaAs衬底等)的调制信号.来自表面量子点本身的调制信号是多个清晰的调制峰.用一阶和三阶微分洛伦兹线形对PzR谱中对应结构的实验数据进行了拟合，精确确定了与样品的各个组成结构相对应的调制峰的能量位置.对不同样品PzR谱的差异进行了定性的说明. 关键词： 压电调制光谱 InAs/GaAs 表面量子点 洛伦兹线形拟合     

反应磁控溅射ZnO/MgO多量子阱的光致荧光光谱分析

采用反应射频磁控溅射方法，在Si(001)基片上制备了具有高c轴择优取向的ZnO/MgO多量子阱.利用X射线反射、X射线衍射、电子探针，光致荧光光谱等表征技术，研究了ZnO/MgO多量子阱的结构、成份和光致荧光特性.研究结果表明，多量子阱的调制周期在1.85—22.3 nm之间，所制备的多量子阱具有量子限域效应，导致了室温光致荧光峰的蓝移，并观测到了量子隧穿效应引起的荧光效率下降.建立了基于多声子辅助激子复合跃迁理论的室温光致荧光光谱优化拟合方法，通过室温光致荧光光谱拟合发现，ZnO/MgO比ZnO/ZnMgO多量子阱具有更大的峰位蓝移，探讨了导致光致荧光光谱展宽的可能因素. 关键词： ZnO/MgO 多量子阱 磁控溅射 光致荧光 量子限域效应     

稀掺杂GaNxAs1－x(x≤0.03)薄膜的调制光谱研究

利用室温下压电调制反射光(PzR)谱技术系统测量了N掺杂浓度为0.0%—3%的分子束外延生长GaN_xAs_1-x薄膜，并对图谱中所观察的光学跃迁进行了指认.在GaN_0.005As_0.995和GaN_0.01As_0.99薄膜的PzR谱中观察到此前只在椭圆偏振谱中才看到的N掺杂相关能态E₁+Δ₁+Δ_N.当N掺杂浓度达到 关键词： 压电调制反射光谱(PzR) xAs_1-x薄膜')" href="#">GaN_xAs_1-x薄膜 分子束外延(MBE)     

量子限制受主的光致发光研究

对一系列δ掺杂浅受主铍（Be）原子的GaAs/AlAs多量子阱和均匀掺杂Be受主的GaAs体材料中Be原子的能级间跃迁进行了光致发光（PL）研究.实验中所用的样品是通过分子束外延技术生长的均匀掺杂Be受主的GaAs外延单层样品和一系列GaAs/AlAs多量子阱样品,并在每量子阱中央进行了Be原子的δ掺杂,量子阱宽度为30 到200 ?.在4.2 K温度下测量了上述系列样品的光致发光谱,清楚地观察到了束缚激子的受主从基态1s_3/2（Γ₆）到第一激发态 关键词： 量子限制受主 光致发光 多量子阱 δ掺杂     

谱导数法在光谱研究GaInAs/InP和GaInP/AlGaInP多量子阱中的应用

在简要讨论谱导数法物理机理的基础上, 给出了其在光吸收谱和光反射谱方法研究张应变GaInAs/InP和GaInP/AlGaInP多量子阱中的成功应用实例. 比较了不同阶谱导数对测定激子跃 迁能量的影响，论及了其与双调制谱方法、曲线拟合方法的区别. 指出了谱导数法在光谱研 究GaInAs/InP和GaInP/AlGaInP多量子阱中的重要性和易行性. 关键词： 谱导数法 吸收谱 反射谱 多量子阱 激子     

用深能级瞬态谱方法研究赝晶Si/Ge0.25Si0.75/Si单量子阱的价带偏移

应变的Ge_xSi_1-x层和未应变的硅层间的能带偏移主要是价带偏移。量子阱中载流子的热发射能与界面的能带偏移有着密切的关系。本文用深能级瞬态谱(DLTS)研究分子束外延生长的p型Si/Ge_0.25Si_0.75/Si单量子阱的价带偏移,阱宽为15nm,考虑到电场的影响和量子阱中第一子能级的位置,对从DLTS得到的热发射能进行适当的修正,可以计算出Si/Ge_0.25Si_0.75/S 关键词：     

Electron-density-dependent optical spectra of a remotely-doped GaAs/Al0.33Ga0.67As single quantum well

We have measured electroreflectance (ER) and photoluminescence (PL) spectra of a high-quality remotely-doped GaAs/Al_0.33Ga_0.67As quantum well (QW) as a function of electron density. Both techniques show the transition from the electron Fermi energy to the ground hole subband, although it is enhanced in ER due to its strong blue shift with electron density. The negligible Stokes shift of the transition demonstrates that the holes involved in the recombination are not strongly localised, consistent with the absence of a distinct peak due to the Fermi edge singularity. The ER spectra show in addition several transitions from the Fermi energy to excited hole subbands. Transitions involving the second and third electron subbands shift to lower energy with electron density due to both the Stark shift induced by the charge in the QW and bandgap renormalisation, which we compare to calculations.     

Upconversion of photoluminescence due to subband resonances in a GaAs/AlAs multiple quantum well structure

We have investigated the upconversion of photoluminescence (PL) due to subband resonances in a simple GaAs(15.3 nm)/AlAs(4.5 nm) multiple quantum well embedded in a p–i–n diode structure. The systematic measurements of the PL spectra and the calculated results of the interband transition energies as a function of electric field strength reveal that the PL bands from the electron subbands with n=3 (E3) and n=4 (E4) sharply appear under the first-nearest-neighbor resonance conditions between the E1 and E3 subbands and the E1 and E4 subbands, respectively, owing to the carrier injection to the E3 and E4 subbands from the E1 subband. This result indicates that the resonant tunneling due to the subband resonance is a dominant mechanism for the carrier population in the higher lying subbands. Utilizing these subband resonances, we have demonstrated the upconversion of PL from the E3 and E4 subbands under the excitation condition of the fundamental interband transition between the E1 and the n=1 heavy-hole subbands.     

用光伏谱方法研究InGaAs/GaAs应变量子阱的性质

采用低温光伏谱方法，研究了应变In_0.18Ga_0.82/GaAs单量子阱结构中各子能级之间的光跃迁，并与理论计算的结果进行比较，对光伏谱的谱峰跃迁能量随温度变化的分析，表明量子阱中的应变与温度基本无关．研究了光伏谱的谱峰半高宽度随温度的变化关系．讨论了声子关联、混晶组分起伏及生长界面不平整对光伏谱谱峰宽度的影响 关键词：     

Electroreflectance studies of thin GaAs/AlGaAs quantum well structures with tunable 2DEG densities

We report the results of low-temperature electroreflectance (ER) and photoluminescence (PL) investigations on thin n-type modulation-doped GaAs/AlGaAs single quantum well structures. The density of the two-dimensional electron gas (2DEG) is varied continuously from zero to N_s∼6*10¹¹ cm^-2, using a Schottky gate, and is detected optically via the Stokes shift between the ER and PL subband transitions. For the first time, the splitting between transitions involving the first electron subband and the first heavy and light hole subbands, respectively, is studied as a function of the 2DEG density using ER spectroscopy. The results are discussed in comparison with the calculated in-plane dispersion of the hole subbands. Clear evidence is given for the influence of exciton screening effects.     

Band offsets in In0.15Ga0.85As/ GaAs and In0.15Ga0.85As/Al0.15Ga0.85As studied by photoluminescence and cathodoluminescence

Photoluminescence and cathodoluminescence measurements of strained undoped In_0.15Ga_0.85As/GaAs and In_0.15Ga_0.85As/Al_0.15Ga_0.85As quantum well structures with emission lines attributed to the first electron–first heavy hole and first electron–first light hole excitonic transitions have been analysed theoretically within the eight-band effective mass approximation. For In_0.15Ga_0.85As/GaAs the results are consistent with either type I or type II alignment of the light hole band. In the case of In_0.15Ga_0.85As/Al_0.15Ga_0.85As our results indicate type II alignment for the light hole band and offset ratio ofQ = 0.83.     

Shake-up intersubband transitions observed in GaAs/AlGaAs quantum wells

Shake-up transitions involving QW hole subbands have been observed as satellites in selective photoluminescence spectra of undoped GaAs/AlGaAs QWs. These shake-up transitions are explained in terms of an interaction between localized exciton and valence-band hole states attached to the QW subbands, in which holes are shaken up from the n=1 heavy hole subband to higher subbands, either the n=1 light hole subband or the n=2 heavy hole subband. The required localization is due to the interface roughness; thus these new transitions are of intrinsic origin. From the observation of the intersubband shake-up processes we derive direct information about the hole inter-subband energies. Furthermore, the satellite intensity is strikingly enhanced in the presence of a magnetic field due to an increasing exciton localization related to the compression of its wave function in the field. The exciton wave function compression continues until its radius in the plane of the well is comparable with the radius of the "flat island" characterized by constant QW width. Accordingly, from the magnetic field dependence of the shake-up satellite intensity we can roughly estimate the size of the "flat islands" and consequently probe the interface roughness.     

GaAs/AlxGa1-xAs量子阱红外探测器微结构研究

采用金属有机物化学气相沉积法生长了两种不同结构参数GaAs/AlxGa1-xAs量子阱材料。利用傅里叶光谱仪分别对势垒中Al组分为0.20,0.30的1#,2#样品进行77 K液氮温度下光谱响应测试。结果显示:1#,2#峰值响应波长为8.38,7.59 m,而根据薛定谔方程得到峰值波长为9.694,8.134 m,二者误差分别为13.6%,6.68%。针对误差过大及吸收峰向高能方向发生漂移的现象,利用高分辨透射扫描电镜对样品微观界面结构进行分析,结果显示,样品存在不同程度的位错及不均匀性。结果表明:位错引起AlGaAs与GaAs晶格不匹配,是造成1#误差较大的主要原因;峰值响应波长随势垒中Al组分的降低而增大,说明Al组分减小致使量子阱子带间距离缩小是导致峰值响应波长红移的原因。     

Modification of the energy spectrum and magnetic breakdown in a system of 2D holes at the GaAs/Al<Subscript>0.5</Subscript> Ga<Subscript>0.5</Subscript>As heterojunction upon uniaxial compression

Uniaxial compression of the p-type GaAs/Al_0.5Ga_0.5 As heterostructures induces magnetic breakdown between the spin-split ground-state subbands of two-dimensional heavy holes. This phenomenon serves as direct experimental evidence of a strong qualitative modification of the energy spectrum of these structures upon uniaxial deformation. This modification has been revealed by numerical calculations, and, according to it, the subband spin splitting decreases upon compression, while the contours of the hole Fermi surface in both subbands touch one another in the compression direction in a pressure range of 2.5 kbar.     

In0.53Ga0.47As/In0.52Al0.48As量子阱中的正磁电阻效应

在低温强磁场条件下,对In_0.53Ga_0.47As/In_0.52Al_0.48As量子阱中的二维电子气进行了磁输运测试.在低磁场范围内观察到正磁电阻效应,在高磁场下这一正磁电阻趋于饱和,分析表明这一现象与二维电子气中的电子占据两个子带有关.在考虑了两个子带之间的散射效应后,通过分析低磁场下的正磁电阻,得到了每个子带电子的迁移率,结果表明第二子带电子的迁移率高于第一子带电子的迁移率.进一步分析表明,这主要是由两个子带之间的 关键词： 二维电子气 正磁电阻 子带散射     

Contactless electroreflectance of GaNyAs1−y/GaAs multi quantum wells: The conduction band offset and electron effective mass issues

Interband transitions in GaN_yAs_1−y/GaAs multi quantum well (MQW) samples with y=0.012 and 0.023 have been studied by contactless electroreflectance spectroscopy (CER). Optical transitions related to absorption in the GaAs barriers and in the GaN_yAs_1−y/GaAs QWs have been observed and analyzed. The GaAs related transition exhibits clear Franz-Keldysh oscillations with the period corresponding to the built-in electric field of 14 and 17 kV/cm for samples with y=0.012 and 0.023, respectively. The portion of the CER spectrum related to absorption in the GaN_yAs_1−y/GaAs QW exhibits two clear resonances which are attributed to optical transitions between the ground and excited states confined in the QWs. The resonance attributed to the ground state transition is associated with absorption between the first light- and heavy-hole subbands and the first electron subband (11L and 11H) while the resonance attributed to the excited state transition is associated with absorption between the second heavy-hole subband and the second electron subband (22H). The energies of the 11H and 22H transitions have been matched with those obtained from theoretical calculations performed within the effective mass approximation. Thus, the GaN_yAs_1−y/GaAs QWs are type-I structures with a conduction band offset, Q_C, between 70 and 80%. Moreover, the incorporation of N atoms into GaAs is found to cause a significant increase in the electron effective mass. The determined values of electron effective mass for GaN_yAs_1−y/GaAs QW with y=0.012 and 0.023 are 0.105m₀ and 0.115m₀, respectively.