Prominent resonance Raman and photoluminescence spectroscopic differences between AA′ and AB stacked bilayer molybdenum disulfide (MoS2) grown by chemical vapor deposition are reported. Bilayer MoS2 islands consisting of the two stacking orders were obtained under identical growth conditions. Resonance Raman and photoluminescence spectra of AA′ and AB stacked bilayer MoS2 were obtained on Au nanopyramid surfaces under strong plasmon resonance. Both resonance Raman and photoluminescence spectra show distinct features indicating clear differences in interlayer interaction between these two phases. The implication of these findings on device applications based on spin and valley degrees of freedom will be discussed.

Buried-channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 10 5 cm 2 V −1 s −1 ) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top-gate of a dopant-less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 10 11 cm −2 , light effective mass (0.09m e ), and high effective g-factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies.

In this letter we report on a metal–semiconductor–metal photodetector based on thick relaxed Ge layers, epitaxially grown on silicon after insertion of a low-temperature-grown Ge buffer layer. The detector shows a good responsivity at normal incidence at both 1.3 and 1.55 μm, with a maximum responsivity of 0.24 A/W at 1.3 μm under a 1 V bias. A response time of about 2 ns has been measured.

Superconductors and semiconductors are crucial platforms in the field of quantum computing. They can be combined to hybrids, bringing together physical properties that enable the discovery of new emergent phenomena and provide novel strategies for quantum control. The involved semiconductor materials, however, suffer from disorder, hyperfine interactions or lack of planar technology. Here we realise an approach that overcomes these issues altogether and integrate gate-defined quantum dots and superconductivity into germanium heterostructures. In our system, heavy holes with mobilities exceeding 500,000 cm2 (Vs)−1 are confined in shallow quantum wells that are directly contacted by annealed aluminium leads. We observe proximity-induced superconductivity in the quantum well and demonstrate electric gate-control of the supercurrent. Germanium therefore has great promise for fast and coherent quantum hardware and, being compatible with standard manufacturing, could become a leading material for quantum information processing.

We have applied atomic force microscopy and x-ray photoemission spectroscopy to the study of\ud SiGe intermixing in Ge/Si~100! self-assembled islands. We have quantified the Ge/Si alloying as a\ud function of the deposition temperature in the 500–850 °C range. The Si content inside the islands varies from 0% at 550 °C up to 72% at 850 °C. As a consequence of the reduction of the effective mismatch due to the observed SiGe intermixing, the critical base width for island nucleation increases from 25 nm for Tdep,600 °C up to 270 nm for Tdep5850 °C

GeSn and SiGeSn are promising materials for the fabrication of a group IV laser source offering a number of design options from bulk to heterostructures and quantum wells. Here, we investigate GeSn/SiGeSn multi quantum wells using the optically pumped laser effect. Three complex heterostructures were grown on top of 200 nm thick strain relaxed Ge0.9Sn0.1 buffers. The lasing is investigated in terms of threshold and maximal lasing operation temperature by comparing multiple quantum well to double heterostructure samples. Pumping under two different wavelengths of 1064 nm and 1550 nm yield comparable lasing thresholds. The design with multi quantum wells reduces the lasing threshold to (40 ± 5) kW/cm 2 at 20 K, almost 10 times lower than for bulk structures. Moreover, 20 K higher maximal lasing temperatures were found for lower energy pumping of 1550 nm.

No abstract

In this work we study, using experiments and theoretical modeling, the mechanical and optical properties of tensile strained Ge microstructures directly fabricated in a state-of-the art complementary metal-oxide-semiconductor fabrication line, using fully qualified materials and methods. We show that these microstructures can be used as active lasing materials in mm-long Fabry-Perot cavities, taking advantage of strain-enhanced direct band gap recombination. The results of our study can be realistically applied to the fabrication of a prototype platform for monolithic integration of near infrared laser sources for silicon photonics.