量子限制受主远红外电致发光器件的制备与测量

采用分子束外延技术生长GaAs/AlAs三量子阱,并在中间的GaAs阱中δ-掺杂浅受主杂质Be原子,制作出量子限制受主远红外Teraherz原型电致发光器件.实验上测量得到4.5 K时器件的电致发光谱（EL）和电传输特性（I-V曲线）.在EL发射谱中清楚地观察到222 cm^-1处宽的尖峰,这来源于Be受主奇宇称激发态到其基态的辐射跃迁,而非辐射弛豫过程则使发射谱的信号很弱.另外在I-V曲线中072和186 V的位置出现两个共振隧道贯穿现象,分别对应于中间δ-掺杂量子阱受主能级1s_3/2(Γ₆+Γ₇)到左边非掺GaAs量子阱中HH带,及右边非掺杂GaAs量子阱中HH重空穴带到中间掺杂GaAs量子阱中Be受主杂质原子奇宇称激发态2p_5/2(Γ₆+Γ₇)能级的共振隧穿.     

GaAs/AlAs量子阱中受主束缚能和光致发光

从实验和理论上,研究了量子限制效应对GaAs/AlAs多量子阱中受主对重空穴束缚能的影响。实验中所用的样品是通过分子束外延生长的一系列GaAs/AlAs多量子阱,量子阱宽度为3~20nm,并且在量子阱中央进行了浅受主Be原子的δ-掺杂。在4,20,40,80,120K不同温度下,分别对上述样品进行了光致发光谱测量,观察到了受主束缚激子从基态到激发态的两空穴跃迁,并且从实验上测得了在不同量子阱宽度下受主的束缚能。理论上应用量子力学中的变分原理,数值计算了受主对重空穴束缚能随量子阱宽度的变化关系,比较发现,理论计算和实验结果符合地较好。     

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     

基于量子限制的受主带间跃迁太赫兹探测器的制备与测量

使用分子束外延生长设备,在GaAs（100）衬底上生长了量子阱宽度为3 nm的GaAs/AlAs多量子阱样品,并在量子阱层中央进行了Be受主的δ-掺杂。根据量子限制受主从束缚态到非束缚态之间的跃迁,设计并制备了δ-掺杂Be受主GaAs/AlAs多量子阱太赫兹光探测器原型器件。在4.2 K温度下,分别对器件进行了太赫兹光电流谱和暗电流-电压曲线的测量。在6 V直流偏压下,空穴载流子沿量子阱层方向输运。当正入射激光频率为6.8 THz时,器件响应率为2×10^-4 V/W（2 μA/W）。通过器件的暗电流-电压曲线计算了器件全散粒噪声电流,在4.2 K、6 V直流偏压下,全散粒噪声电流为5.03 fA·Hz^-1/2。     

量子阱结构对有机电致发光器件效率的影响

实验中共制备了五种有机量子阱结构电致发光器件,分别对这五种量子阱结构器件的电致发光特性进行了研究,分析了量子阱结构的周期数和势垒层的厚度对器件电学性能的影响.实验结果表明适当周期数的量子阱结构器件的亮度和电流效率比传统的三层结构器件的要大,主要原因是量子阱结构对电子和空穴的限制作用,这种限制作用提高了电子和空穴在发光层中形成激子和复合的概率,从而提高了发光的亮度和效率.当改变阱结构器件中势阱层的厚度时,也会对器件的亮度和效率产生影响,采用适当的势阱层厚度能够提高器件的亮度和效率. 关键词： 量子阱结构 电致发光 电流效率 光谱     

量子限制效应对δ掺杂GaAs/AlAs多量子阱中铍受主态寿命的影响

采用远红外时间分辨光谱,研究了量子限制效应对δ掺杂在GaAs/AlAs多量子阱中铍（Be）受主态寿命的影响.在低温下的远红外吸收谱中,清楚地观察到了三条主要吸收线,它们分别来源于铍受主从基态到它的三个奇宇称激发态的跃迁.实验结果表明：随着量子限制效应的增强,受主激发态寿命而减少,实验测得体材料中Be受主2p激发态的寿命是350 ps,而阱宽10 nm的多量子阱中的寿命是55 ps.量子限制效应对布里渊区折叠声学声子模的影响增强了受主带内空穴与声学声子相互作用,从而加快了受主带内空穴的弛豫过程. 关键词： 量子限制效应 受主态寿命 时间分辨光谱 δ掺杂')" href="#">δ掺杂     

能级填充对量子阱光学性质的影响

在特殊设计的三势垒双势阱结构中，利用来自发射极的电子注入和电子向收集极的共振隧穿 逃逸调控量子阱不同子能级上的填充状态，发现激发态上的电子占据起抑制量子限制Stark 效应的作用.在极低偏压下，量子阱中少量过剩电子诱发了用简单带—带跃迁无法解释的光致发光光谱行为. 关键词： 共振隧穿 光致发光 量子限制Stark效应 过剩电子     

量子限制斯达克效应对三角形量子阱吸光特性的影响

本文通过计算量子力学波动方程以及载流子传输特性,哈密顿量的H能谱图和边界条件等的理论方法来分析量子限制斯达克效应对三角形量子阱体系吸收特性的影响,说明了选择合适的量子阱垒层对于提高三角形量子阱吸光率具有重要的意义。     

Far-infrared absorption studies of Be acceptors in δ-doped GaAs/AlAs multiple quantum wells

We report a far-infrared absorption study of internal transitions of shallow Be acceptors in both bulk GaAs and a series of δ-doped GaAs/AlAs multiple quantum well samples with well thicknesses of 20, 15 and 10 nm. Low temperature far-infrared absorption measurements clearly show three principal absorption lines due to transitions of Beacceptor states from the ground state to the first three odd-parity excited states, respectively. Using a variational principle, the 2p-1s transition energies of quantum confined Be acceptors are calculated as a function of the well width. It is found that the theoretical calculation of the 2p_z → 1s transitions is in good agreement with the D-like line experimental data.     

Potential‐inserted quantum well design for quantum cascade terahertz lasers

We report on a new design of terahertz quantum cascade laser based on a single, potential‐inserted quantum well active region. The quantum well properties are engineered through single monolayer InAs inserts. The modeling is based on atomistic, spds* tight‐binding calculations, and performances are compared to that of the classical three‐well design. We obtain a 100% increase of the oscillator strength per unit length, while maintaining a high, nearly temperature‐independent contrast between phonon‐induced relaxation times of the upper and lower lasing states. The improved performances are expected to allow THz lasing at room temperature.     

Mid/far-infrared photo-detectors based on graphene asymmetric quantum wells

We conducted a theoretical study on the electronic properties of a single-layer graphene asymmetric quantum well.Quantification of energy levels is limited by electron–hole conversion at the barrier interfaces and free-electron continuum.Electron–hole conversion at the barrier interfaces can be controlled by introducing an asymmetry between barriers and taking into account the effect of the interactions of the graphene sheet with the substrate.The interaction with the substrate induces an effective mass to carriers,allowing observation of Fabry–P′erot resonances under normal incidence and extinction of Klein tunneling.The asymmetry,between barriers creates a transmission gap between confined states and free-electron continuum,allowing the large graphene asymmetric quantum well to be exploited as a photo-detector operating at mid-and far-infrared frequency regimes.     

Observation of the Fermi-edge singularity in n-doped single asymmetric quantum wells: the influence of residual acceptors

The investigation of the evolution of the photoluminescence spectra, in single asymmetric quantum wells (SAQWs), from a typical emission spectrum to a Fermi-edge singularity, is carried out as a function of both the optical excitation intensity and the temperature. The three samples used here are n-doped, low carrier density (below 5×10¹¹ cm⁻²), GaAs/Al_0.35Ga_0.65As SAQWs grown by molecular beam epitaxy. The strong collective recombination of electrons with different k states up to the Fermi wave vector as well as the optical signature of the Fermi-edge singularity is observed in two samples containing residual acceptors inside the GaAs SAQW. In contrast, a third sample containing no experimental evidence of residual acceptors in the GaAs SAQW shows no optical signature of the Fermi-edge singularity.     

Tight-binding study of quantum transport in nanoscale GaAs Schottky MOSFET

This paper explores the band structure effect to elucidate the feasibility of an ultra-scaled GaAs Schottky MOSFET (SBFET) in a nanoscale regime. We have employed a 20-band sp3d5s* tight-binding (TB) approach to compute E K dispersion. The considerable difference between the extracted effective masses from the TB approach and bulk values implies that quantum confinement affects the device performance. Beside high injection velocity, the ultra-scaled GaAs SBFET suffers from a low conduction band DOS in the Γ valley that results in serious degradation of the gate capacitance. Quantum confinement also results in an increment of the effective Schottky barrier height (SBH). Enhanced Schottky barriers form a double barrier potential well along the channel that leads to resonant tunneling and alters the normal operation of the SBFET. Major factors that may lead to resonant tunneling are investigated. Resonant tunneling occurs at low temperatures and low drain voltages, and gradually diminishes as the channel thickness and the gate length scale down. Accordingly, the GaAs (100) SBFET has poor ballistic performance in nanoscale regime.