Optical beam-induced scattering mode of mid-IR laser microscopy: a method for defect investigation in near-surface and near-interface regions of bulk semiconductors
This paper presents a new technique of optical beam-induced scattering of mid-IR-laser radiation, which is a special mode of the recently developed scanning mid-IR-laser microscopy. The technique in its present form is designed for investigation of large-scale recombination-active defects in near-surface and near-interface regions of semiconductor wafers. However, it can be easily modified for the defect investigations in the crystal bulk. Being in many respects analogous to EBIC, the present technique has some indisputable advantages, which enable its application for both non-destructive laboratory investigations and quality monitoring in the industry.
Scanning Tunneling Microscopy of Defect States in the Semiconductor Bi$_2$Se$_3$
Bi $_2$ Se $_3$掺杂过量Bi的扫描隧道光谱图像揭示了具有类似三叶草叶子的引人注目的形状的电子缺陷状态。用一个简单的紧束缚模型，我们表明，在Bi $_2$ Se $_3$的缺陷态的几何形状可以直接相关的位置的起源杂质。只有Bi缺陷的Se网站五个原子层以下的表面实验观察到。我们发现，这种效果可以解释的缺陷和表面电子结构的相互作用。
The mid-infrared (MIR), far-infrared (FIR) to terahertz (THz) frequencies are the least developed parts of the electromagnetic spectrum for applications. Traditional semiconductor technologies like laser diodes and photodetectors are successful in the visible light range, but are still confronted with great challenges when extended into the MIR/FIR/THz range. In this paper, we demonstrate that topological insulators (TIs), especially those with Mexican-hat band structure (MHBS), provide a route to overcome these challenges. The optical responses of MHBS TIs can be one to two orders of magnitud…
Plasmonic-cavity Modulator for the Mid-IR with a Semi-transparent and Nonlinear Heavily-doped Semiconductor Mirror
Istituto Italiano di Tecnologia（意大利理工学院）；Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche（国家研究委员会光子和纳米技术研究所）；University of Luxembourg（卢森堡大学）；Institute for Advanced Studies, University of Luxembourg Campus Belval（卢森堡大学贝尔瓦尔校区高等研究院）；Centre de Nanosciences et de Nanotechnologies (C2N), CNRS UMR 9001, Universit´e Paris-Saclay（巴黎萨克雷大学CNRS 9001联合实验室纳米科学与纳米技术中心）
By independently engineering strain and composition, this work demonstrates and investigates direct band gap emission in the mid-infrared range from GeSn layers grown on silicon. We extend the room-temperature emission wavelength above ~4.0 μm upon post-growth strain relaxation in layers with uniform Sn content of 17 at.%. The fundamental mechanisms governing the optical emission are discussed based on temperature-dependent photoluminescence, absorption measurements, and theoretical simulations. Regardless of strain and composition, these analyses confirm that single-peak emission is always ob…
Acousto-optical devices, such as modulators, filters or deflectors, implement a simple and effective way of light modulation and signal processing techniques. However, their operation wavelengths are restricted to visible and near-infrared frequency region due to a quadratic decrease of the efficiency of acousto-optical interaction with the wavelength increase. At the same time, almost all materials with high value of acousto-optic figure of merit are non-transparent at wavelengths larger than 5 μm, while the transparent materials possess significantly lower acousto-optic figure of merit. Here…
Energy carrier transport and recombination in emerging semiconductors can be directly monitored with optical microscopy, leading to the measurement of the diffusion coefficient (D), a critical property for design of efficient optoelectronic devices. D is often determined by fitting a time-resolved expanding carrier profile after optical excitation using a Mean Squared Displacement (MSD) Model. Although this approach has gained widespread adoption, its utilization can significantly overestimate D due to the non-linear recombination processes that artificially broaden the carrier distribution pr…
We study high order harmonics generation (HHG) in crystalline silicon and diamond subjected to near and mid-infrared laser pulses. We employ time-dependent density functional theory and solve the time-dependent Kohn-Sham equation in the single-cell geometry. We demonstrate that clear and clean HHG spectra can be generated with careful selection of the pulse duration. In addition, we simulate dephasing effects in a large silicon super-cell through displacement of atomic positions prepared by a molecular dynamics simulation. We compare our results with the previous calculations by Floss et al. […
The present paper is dedicated to the structural study of crystallographic peculiarities appearing in epitaxial films of metastable epsilon iron oxide ($\varepsilon$-Fe$_2$O$_3$) grown by pulsed laser deposition onto a semiconductor GaN (0001) substrate. The columnar structure of the nanoscale $\varepsilon$-Fe$_2$O$_3$ films has been for the first time investigated using high resolution electron microscopy (HRTEM) direct space technique complemented by reciprocal space methods of high-energy electron diffraction and color-enhanced HRTEM image Fourier filtering. The study of $\varepsilon$-Fe$_2…
Theory and design of In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ mid-infrared semiconductor lasers: type-I quantum wells for emission beyond 3 $μ$m on InP substrates
我们提出了一个理论分析和优化的中红外半导体激光器的属性和性能的基础上稀释bismide合金在$_{x}$ Ga $_{1-x}$作为$_{1-y}$ Bi $_{y}$，生长在传统的（001）InP衬底。在这种四元合金中独立地改变外延应变和发射波长的能力为带结构工程提供了显著的范围。我们的计算表明，基于压缩应变的In $_{x}$ Ga $_{1-x}$ As $_{1-y}$ Bi $_{y}$量子阱（QW）的结构可以容易地实现在3 - 5 $μ$ m范围内的发射波长，并且这些QW具有大的I型带偏移。因此，这些结构具有克服通常与这种应用丰富但技术上具有挑战性的波长范围相关联的许多限制的潜力。通过考虑具有（i）固定QW厚度和可变应变，以及（ii）固定应变和可变QW厚度的结构，我们将特性和性能的关键趋势量化为合金成分，结构特性和发射波长的函数，并在此基础上确定实现实际应用的优化器件的路线。我们的分析表明，简单的激光器结构-将在$_{x}$镓$_{1-x}$作为$_{1-y}$铋$_{y}$量子阱和无应变三元在$_{0.53}$镓$_{0.47}$作为障碍-这是与既定的外延生长兼容，提供了一条路线，以实现基于InP的中红外二极管激光器。
One primary concern in diluted magnetic semiconductors (DMSs) is how to establish a long-range magnetic order with a low magnetic doping concentration to maintain the gate tunability of the host semiconductor, as well as to increase Curie temperature. Two-dimensional van der Waals semiconductors have been recently investigated to demonstrate the magnetic order in DMSs; however, a comprehensive understanding of the mechanism responsible for the gate-tunable long-range magnetic order in DMSs has not been achieved yet. Here, we introduce a monolayer tungsten diselenide (WSe2) semiconductor with V…
Interface effects on an ultrathin Co film in multilayers based on the organic semiconductor Alq3
利用原子力显微镜、SQUID磁谱仪和核磁共振（NMR）研究了AlOx阻挡层厚度对Ta/Co/（AlOx）/Alq 3/Si混合结构磁性能和形貌的影响。所有使用的技术都指出，需要2nm的阻挡层厚度来在Alq 3的顶部上获得磁性良好的钴层。59 Co NMR测量结果表明，AlOx阻挡层导致形成具有“缺陷”钴的界面层，有利于具有良好磁性能的“大块”钴的生长。
Strain engineering has been a ubiquitous paradigm to tailor the electronic band structure and harness the associated new or enhanced fundamental properties in semiconductors. In this regard, semiconductor membranes emerged as a versatile class of nanoscale materials to control lattice strain and engineer complex heterostructures leading to the development of a variety of innovative applications. Herein we exploit this quasi-two-dimensional platform to tune simultaneously the lattice parameter and bandgap energy in group IV GeSn semiconductor alloys. As Sn content is increased to reach a direct…
Atomically thin binary 2-dimensional (2D) semiconductors exhibit diverse physical properties depending on their composition, structure and thickness. By adding another element in those materials, which will lead to formation of ternary 2D materials, the property and structure would greatly change and significantly expanded applications could be explored. In this work, we report structural and optical properties of atomically thin chromium thiophosphate (CrPS4), a ternary antiferromagnetic semiconductor. Its structural details were revealed by X-ray and electron diffractions. Transmission elect…
Combining scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we demonstrate how to tune the doping of epitaxial graphene from p to n by exploiting the structural changes that occur spontaneously on the Ge surface upon thermal annealing. Furthermore, using first principle calculations we build a model that successfully reproduces the experimental observations. Since the ability to modify graphene electronic properties is of fundamental importance when it comes to applications, our results provide an important contribution towards the integration of graphene with conven…
Epitaxial Al/GaAs/Al structures having controlled thickness of high-quality GaAs and pristine interfaces have been fabricated using a wafer-bonding technique. III-V semiconductor/Al structures are grown by molecular beam epitaxy on III-V semiconductor substrates and bonded to silicon and sapphire. Selective etching is used to remove the III-V substrate followed by surface cleaning and superconductor regrowth, resulting in epitaxial Al/GaAs/Al tri-layers on sapphire or silicon substrates. Structures are characterized with reflection high energy electron diffraction, atomic force microscopy, X-r…
Understanding the interplay between the structure, composition and opto-electronic properties of semiconductor nano-objects requires combining transmission electron microscopy (TEM) based techniques with electrical and optical measurements on the very same specimen. Recent developments in TEM technologies allow not only the identification and in-situ electrical characterization of a particular object, but also the direct visualization of its modification in-situ by techniques such as Joule heating. Over the past years, we have carried out a number of studies in these fields that are reviewed i…
