共振声子辅助的太赫兹量子级联激光器中杂质散射的蒙特卡洛模拟

通过蒙特卡洛方法研究了基于共振声子散射的太赫兹量子级联激光器中杂质散射对激光器性能的影响.使用单子带静态屏蔽模型来处理电子与杂质的散射过程.发现电子与杂质的散射为电子在有源区中的注入和抽取过程提供了另外一个通道.这一过程可以影响电子在不同子带的占据数以及器件的电流.所以,在考虑基于共振声子散射的太赫兹量子级联激光器中的电子输运过程时,需要包含电子与杂质的散射过程.     

Monte Carlo Simulation of Impurity Scattering Effect in Resonant-Phonon-Assisted Terahertz Quantum-Cascade Lasers

通过蒙特卡洛方法研究了基于共振声子散射的太赫兹量子级联激光器中杂质散射对激光器性能的影响.使用单子带静态屏蔽模型来处理电子与杂质的散射过程.发现电子与杂质的散射为电子在有源区中的注入和抽取过程提供了另外一个通道.这一过程可以影响电子在不同子带的占据数以及器件的电流.所以,在考虑基于共振声子散射的太赫兹量子级联激光器中的电子输运过程时,需要包含电子与杂质的散射过程.     

共振声子THz QCL有源区结构设计

利用Airy函数代换与传输矩阵方法精确计算了有外加偏压下电子在共振声子太赫兹量子级联激光器有源区单个周期内的透射系数与波函数,得到了不同偏压下的电子波函数分布以及准束缚态能级位置与外加偏压的关系曲线.在仿真计算的基础上设计了一种共振声子太赫兹量子级联激光器的有源区结构.计算结果表明,对于设计的结构,当单个周期两端的外加...     

共振声子太赫兹量子级联激光器研究

针对四阱有源区、一阱注入区及三阱有源设计,采用蒙特卡洛模拟方法研究了共振声子太赫兹量子级联激光器的性能差异。采用傅里叶变换光谱仪及远红外探测器测量了四阱共振声子太赫兹量子级联激光器的低温电光特性。详细讨论了提高太赫兹量子级联激光器发射功率的方案。     

半导体太赫兹源综述

太赫兹技术可以应用于信息科学,生物,医学,天文和环境科学等方面,而太赫兹源是太赫兹应用的关键器件。作者针对半导体太赫兹源如GaAs1-xNx二极管、量子阱负有效质量太赫兹振荡器和太赫兹量子级联激光器做了一个简要的回顾。掺杂的GaAs1-xNx二极管在直流偏压下的电流自振荡行为得到了研究,发现电流自振荡与这种独特材料体系非抛物线型导带的负微分速率效应相关。量子阱负有效质量p pp 二极管通过考虑杂质散射、光学声子和声学声子散射研究了其电流自振荡和瞬时电流形态,研究发现偏压和掺杂浓度会对电流自振荡频率产生很大影响,负有效质量p pp 二极管可以用作可电学调制的太赫兹源。此外,我们通过蒙特卡洛模拟对共振声子结构的太赫兹量子级联激光器进行了器件参数的优化,结果表明注入势垒宽度、掺杂浓度和声子抽取能级差设计对计算增益有很大的影响,我们的计算结果与实验结果一致。     

太赫兹量子级联激光器有源区增益分析和设计

太赫兹量子级联激光器(QCL)有源区设计主要包括啁啾超晶格、束缚-连续态跃迁和共振声子等模式。本文利用密度矩阵方法模拟太赫兹QCL光增益谱的基本特征,特别是通过分析太赫兹QCL光增益特性与子带寿命的依赖关系,理解太赫兹QCL对超晶格子带间非辐射跃迁寿命的要求。进而根据这些要求给出一种基于束缚-连续态跃迁和共振声子混合模式的太赫兹QCL有源区设计方案,利用纵光学声子共振帮助缩短束缚-连续态跃迁模式中下辐射态寿命。     

太赫兹量子级联激光器与量子阱探测器研究进展（特邀）

太赫兹量子级联激光器和太赫兹量子阱探测器都是基于子带间电子跃迁的半导体器件,具有体积小、频率可调、响应速度快等优点。其工作波长位于微波波长和红外波长之间,其光谱涵盖了众多气体分子、化合物以及凝聚态物质的频谱特征,在天文观测、公共安全、生物医药等领域中有重大应用前景。近年来,太赫兹量子级联激光器和太赫兹量子阱探测器的性能有了显著提高,其应用也受到关注。回顾了太赫兹量子级联激光器和量子阱探测器的发展历程,简述了其工作原理和器件结构,介绍了器件性能在工作温度、光谱范围等方面的最新进展及其在高分辨光谱、太赫兹成像、无线宽带通信等方面的应用,并在此基础上分析了目前存在的问题和研究热点,对其未来发展进行了展望。     

太赫兹QCL的电子结构计算和设计

通过电子结构和波函数的设计实现电子选择性注入及粒子数反转是制备太赫兹量子级联激光器(QCL)的基础。本文介绍了求解外场下超晶格QCL电子结构的分区级数解法及非正交基对角化方法,并将计算结果与国际上啁啾超晶格及共振声子模式QCL的相关实验结果进行了对比,二者的精确吻合证明了计算方法的准确性。在此基础上给出了一种共振声子模式QCL超晶格的有源区设计方案,并讨论了外场偏离设计值对QCL特性的影响。     

太赫兹波的几个基本问题

介绍了用于加工太赫兹波元件的微机械加工技术(铣削、放电加工、电铸、湿法腐蚀Si、干法腐蚀Si、厚光刻胶:SU-8和LIGA)及其最新结果。重点描述了应用于太赫兹波的器件和集成电路,如将可用于太赫兹波的各种新颖二极管、半导体纳米器件、新的高电子迁移率晶体管、毫米波集成电路、量子器件、红外器件、量子级联激光器(单极级间跃迁激光器)。基于带间跃迁量子机理的半导体器件(譬如量子级联激光器)的频率极限高于与半导体能带隙相关器件的频率,其大多数体半导体的频率可以达到10THz以上。但是,基于经典的电子扩散传输机理的二极管、三极管的高频极限则受限于渡越时间和寄生参数RC时间常数。     

太赫兹量子级联激光器

太赫兹技术近年来发展迅速,应用越来越广泛,是当前的热门研究领域。太赫兹量子级联激光器是产生太赫兹辐射的重要器件,对太赫兹量子级联激光器的发展,以及有源区和波导层的设计等进行了详细讨论。     

基于多模速率方程电路建模的太赫兹量子级联激光器稳态性能及输出光谱特性分析

通过改进的三能级多模态速率方程,运用电路建模 方法,建立了太赫兹(THz)量子级联激光器(QCL)的一种等效电路模型。由于基于多模 态效应进行建模,所建模型能够有效表 征多模态效应对THz QCL光电性能的影响。模型中,涉及的非辐射散射时间、自激发射弛豫 时间以及电子逃 逸时间均根据器件有源层结构参数通过自洽数值求解获得。采用所建模型,可运用通用电路 仿真工具实现对 THz QCL光电特性的模拟分析,克服了数值分析方法计算复杂、模拟时间长的缺点。运用电 路仿 真工具PSPICE对2.47THz QCL的稳态特性和输出光谱特性进行了模拟 分析,并讨论了温度变化对器 件阈值电流、输出光功率以及输出频谱的影响,分析结果与已报道的理论和实验结果一致 ,验证了本文方法的适用性和准确性。     

宽谱太赫兹量子级联激光器的自混合特性

基于传输矩阵理论及多模速率方程,研究了宽谱太赫兹量子级联激光器在不同光反馈强度下的自混合动力学特性.研究发现,在弱反馈下光场自混合对激光器光谱特性影响很小;反射物位置移动时的自混合信号呈正弦规律变化,同时自混合信号幅度随反射物位置的变化表现出周期性调制现象.宽谱量子级联激光器在弱反馈下可以应用于测距、成像及光谱测量.在...     

Steady-State Electron Transport and Low-Field Mobility of Wurtzite Bulk ZnO and Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O

Steady-state electron transport and low-field electron mobility characteristics of wurtzite ZnO and Zn_1−x Mg _x O are examined using the ensemble Monte Carlo model. The Monte Carlo calculations are carried out using a three-valley model for the systems under consideration. Acoustic and optical phonon scattering, intervalley (equivalent and nonequivalent) scattering, ionized impurity scattering, and alloy disorder scattering are used in the Monte Carlo simulations. Steady-state electron transport is analyzed, and the population of valleys is also obtained as a function of applied electric field and ionized impurity concentrations. The negative differential mobility phenomena is clearly observed and seems compatible with the occupancy and effective nonparabolicity factors of the valleys in bulk ZnO and in Zn_1−x Mg _x O with low Mg content. The low-field mobilities are obtained as a function of temperature and ionized impurity concentrations from the slope of the linear part of each velocity–field curve. It is seen that mobilities begin to be significantly affected for ionized impurity concentrations above 5 × 10¹⁵/cm³. The calculated Monte Carlo simulation results for low-field electron mobilities are found to be consistent with published data.     

High Resolution Terahertz Spectroscopy with Quantum Cascade Lasers

High resolution terahertz (THz) spectroscopy is a powerful analytical tool for laboratory purposes as well as for remote sensing in astronomy, planetary research, and Earth observation. THz quantum cascade lasers (QCLs) are promising sources for implementation into THz spectrometers, in particular at frequencies above 3 THz, which is the least explored portion of the THz region. One application of QCLs in THz spectroscopy is in absorption spectrometers, where they can replace less powerful and somewhat cumbersome sources based on frequency mixing with gas lasers. Another one is using a QCL as local oscillator in a heterodyne spectrometer for remote sensing. This article will review the state-of-the art in high resolution THz spectroscopy with QCLs.     

Band-Like Charge Transport in Phytic Acid-Doped Polyaniline Thin Films

We explore the charge transport properties of phytic acid (PA) doped polyaniline thin films prepared by the surfactant monolayer-assisted interfacial synthesis (SMAIS). Structural and elemental analysis confirms the inclusion of PA in the thin films and reveals a progressive loss of crystallinity with the increase of PA doping content. Charge transport properties are interrogated by time-resolved terahertz (THz) spectroscopy. Notably, independently of doping content and hence crystallinity, the frequency-resolved complex conductivity spectra in the THz region can be properly described by the Drude model, demonstrating band-like charge transport in the samples and state-of-the-art charge carrier mobilities of ≈1 cm²V⁻¹s⁻¹. A temperature-dependent analysis for the conductivity further supports band-like charge transport and suggest that charge carrier mobility is primarily limited by impurity scattering. This work highlights the potential of PA doped polyaniline for organic electronics.     

用三维蒙特卡罗模拟栅-源/漏不对准对体硅FinFET器件性能的影响

We investigate the influence of gate-source/drain(G-S/D) misalignment on the performance of bulk fin field effect transistors(FinFETs) through the three-dimensional(3D) full band Monte Carlo simulator.Several scattering mechanisms,such as acoustic and optical phonon scattering,ionized impurity scattering,impact ionization scattering and surface roughness scattering are considered in our simulator.The influence of G-S/D overlap and underlap on the on-states performance and carrier transport of bulk FinFETs are mainly discussed in our work.Our results show that the on-states currents increase with the increment of G-D/S overlap length and the positions of a potential barrier and average electron energy maximum vary with the G-D/S overlap length.The carrier transport phenomena in bulk FinFETs are due to the effect of scattering and the electric field in the overlap/underlap regime.     

Electron transport in heavily doped bases of InP/GaInAs HBT'sprobed by magneto transport experiments

Magneto transport experiments were carried out to study electron transport in the p-type base of InP/GaInAs heterojunction bipolar transistors (HBT's). Electron minority carrier mobility was measured in the °K for two dopant concentrations in the base. The experimentally obtained mobility is compared to the theoretically predicted one. The scattering mechanisms considered in the calculations are screened ionized impurity scattering, alloy scattering, and coupled plasmon polar optical phonon scattering. The latter is calculated in the random phase approximation. The Boltzman transport equation (BTE) is solved to obtain the ratio between the measured mobility and the drift mobility. Good agreement was obtained between the measured results and the calculated ones for temperatures above 100 °K. At lower temperatures the calculated results differ from the experimental ones, probably due to hot electron effects     

Characterizing the beam properties of terahertz quantum-cascade lasers

Terahertz quantum-cascade lasers (QCLs) are very promising radiation sources for many scientific and commercial applications. Shaping and characterizing the beam profile of a QCL is crucial for any of these applications. Usually the beam profile should be as close as possible to a fundamental Gaussian TEM₀₀ mode. In order to completely characterize the laser beam the power and the wavefront have to be measured. We describe methods for characterizing the beam properties of QCLs. Several QCLs with single-plasmon waveguide and emission frequencies between 2 and 5 THz are investigated. The beam profiles of these lasers are shaped into almost fundamental Gaussian modes using dedicated lenses. The beam propagation factor M² is as low as 1.2. The wavefront is measured along the axis of propagation with a THz Hartmann sensor. Its curvature behaves as expected for a Gaussian beam. The applied methods can be transferred to any other THz beam.