Extended-SWIR High-Speed All-GeSn PIN Photodetectors on Silicon

There is an increasing need for silicon-compatible high bandwidth extended-short wave infrared (e-SWIR) photodetectors (PDs) to implement cost-effective and scalable optoelectronic devices. These systems are quintessential to address several technological bottlenecks in detection and ranging, surveillance, ultrafast spectroscopy, and imaging. In fact, current e-SWIR high bandwidth PDs are predominantly made of III-V compound semiconductors and thus are costly and suffer a limited integration on silicon besides a low responsivity at wavelengths exceeding $2.3 \,\mu$m. To circumvent these challenges, Ge$_{1-x}$Sn$_{x}$ semiconductors have been proposed as building blocks for silicon-integrated high-speed e-SWIR devices. Herein, this study demonstrates a vertical all-GeSn PIN PDs consisting of p-Ge$_{0.92}$Sn$_{0.08}$/i-Ge$_{0.91}$Sn$_{0.09}$/n-Ge$_{0.89}$Sn$_{0.11}$ and p-Ge$_{0.91}$Sn$_{0.09}$/i-Ge$_{0.88}$Sn$_{0.12}$/n-Ge$_{0.87}$Sn$_{0.13}$ heterostructures grown on silicon following a step-graded temperature-controlled epitaxy protocol. The performance of these PDs was investigated as a function of the device diameter in the $10-30 \,\mu$m range. The developed PD devices yield a high bandwidth of 12.4 GHz at a bias of 5V for a device diameter of $10 \,\mu$m. Moreover, these devices show a high responsivity of 0.24 A/W, a low noise, and a $2.8 \,\mu$m cutoff wavelength thus covering the whole e-SWIR range

All-Group IV membrane room-temperature mid-infrared photodetector

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 band gap, these semiconductors become metastable and typically compressively strained. We show that the release and transfer of GeSn membranes lead to a significant relaxation thus extending the absorption wavelength range deeper in the mid-infrared. Fully released Ge$_{0.83}$Sn$_{0.17}$ membranes were integrated on silicon and used in the fabrication of broadband photodetectors operating at room temperature with a record wavelength cutoff of 4.6 $\mu$m, without compromising the performance at shorter wavelengths down to 2.3 $\mu$m. These membrane devices are characterized by two orders of magnitude reduction in dark current as compared to devices processed from as-grown strained epitaxial layers. The latter exhibit a content-dependent, shorter wavelength cutoff in the 2.6-3.5 $\mu$m range, thus highlighting the role of lattice strain relaxation in shaping the spectral response of membrane photodetectors. This ability to engineer all-group IV transferable mid-infrared photodetectors lays the groundwork to implement scalable and flexible sensing and imaging technologies exploiting these integrative, silicon-compatible strained-relaxed GeSn membranes

Acceleration of Python Applications on GPU

Konvenčne sa v oblasti high performance computing (HPC) používajú prekladané jazyky, ako napríklad C++. Skriptovacie jazyky ako Python sú však pohodlnejšie a vývoj aplikácií je v nich rýchlejší a jednoduchší. Táto práca porovnáva jazyky C++ a Python z hľadiska možnosti akcelerácie výpočtov na grafickej karte. Jej cieľom je ukázať, že skriptovacie jazyky sú taktiež použiteľné na implementáciu HPC aplikácií a poukázať na ich výhody a nevýhody oproti prekladaným jazykom. Za týmto účelom je implementovaných niekoľko programov. Tie pozostávajú z niekoľkých menších testovacích programov a jedného väčšieho programu, riešiaceho výpočtovo náročný problém. Implementácie týchto programov v jazykoch C++ a Python sú porovnané ako z hľadiska výkonu, tak z hľadiska náročnosti implementácie.Compiled languages, such as C++, are conventionally used in the field of high performance computing (HPC). However, scripting languages like Python are more convenient and application development is quicker and simpler in these languages. This work compares C++ and Python in terms of the possibilities of computation acceleration on graphics card. Its aim is to show that scripting languages are also suitable for the implementation of HPC applications, and point out their advantages and disadvantages compared to compiled languages. To this purpose, a number of programs have been implemented. Several smaller programs for testing purposes and a larger one, implementing a computationally intensive problem. The implementations of these programs in C++ and Python are compared in terms of performance, as well as difficulty of implementation.

Extended short-wave infrared high-speed all-GeSn PIN photodetectors on silicon

ABSTRACT: There is an increasing need for silicon-compatible high-bandwidth extended-short wave infrared (e-SWIR) photodetectors (PDs) to implement cost-effective and scalable optoelectronic devices. These systems are quintessential to address several technological bottlenecks in detection and ranging, surveillance, ultrafast spectroscopy, and imaging. In fact, current e-SWIR high-bandwidth PDs are predominantly made of III–V compound semiconductors and thus are costly and suffer a limited integration on silicon besides a low responsivity at wavelengths exceeding 2.3 μm. To circumvent these challenges, Ge₁₋ₓSnx semiconductors have been proposed as building blocks for silicon-integrated high-speed e-SWIR devices. Herein, this study demonstrates vertical all-GeSn PIN PDs consisting of p-Ge₀.₉₂Sn₀.₀₈/i-Ge₀.₉₁Sn₀.₀₉/n-Ge₀.₈₉Sn₀.₁₁ and p-Ge₀.₉₁Sn₀.₀₉/i-Ge₀.₈₈Sn₀.₁₂/n-Ge₀.₈₇Sn₀.₁₃ heterostructures grown on silicon following a step-graded temperature-controlled epitaxy protocol. The performance of these PDs was investigated as a function of the device diameter in the 10–30 μm range. The developed PD devices yield a high bandwidth of 12.4 GHz at a bias of 5 V for a device diameter of 10 μm. Moreover, these devices show a high responsivity of 0.24 A/W, a low noise, and a 2.8 μm cutoff wavelength, thus covering the whole e-SWIR range

Structural Basis for Substrate Specificity in Human Monomeric Carbonyl Reductases

Carbonyl reduction constitutes a phase I reaction for many xenobiotics and is carried out in mammals mainly by members of two protein families, namely aldo-keto reductases and short-chain dehydrogenases/reductases. In addition to their capacity to reduce xenobiotics, several of the enzymes act on endogenous compounds such as steroids or eicosanoids. One of the major carbonyl reducing enzymes found in humans is carbonyl reductase 1 (CBR1) with a very broad substrate spectrum. A paralog, carbonyl reductase 3 (CBR3) has about 70% sequence identity and has not been sufficiently characterized to date. Screening of a focused xenobiotic compound library revealed that CBR3 has narrower substrate specificity and acts on several orthoquinones, as well as isatin or the anticancer drug oracin. To further investigate structure-activity relationships between these enzymes we crystallized CBR3, performed substrate docking, site-directed mutagenesis and compared its kinetic features to CBR1. Despite high sequence similarities, the active sites differ in shape and surface properties. The data reveal that the differences in substrate specificity are largely due to a short segment of a substrate binding loop comprising critical residues Trp229/Pro230, Ala235/Asp236 as well as part of the active site formed by Met141/Gln142 in CBR1 and CBR3, respectively. The data suggest a minor role in xenobiotic metabolism for CBR3. ENHANCED VERSION: This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1