M. T. Todaro

Long wavelength emission in InxGa1−xAs quantum dot structures grown in a GaAs barrier by metalorganic chemical vapor deposition

We demonstrate a method to obtain room temperature long wavelength emission from InGaAs quantum dots (QDs) growth directly into a binary GaAs matrix. The wavelength is tuned from 1.26 up to 1.33 μm by varying the V/III ratio during growth of the GaAs cap layer, without using a seeding layer or InGaAs wells. Strong improvement in terms of line-shape narrowing and efficiency is obtained. In addition to the shift in wavelength we observe an impressive reduction of temperature dependent quenching of the emission efficiency, which decreases only by a factor of 3 between cryogenic temperatures and room temperature, very good for QD structures emitting at 1.3 μm. Photoluminescence spectroscopy and theoretical modeling were combined for interpretation of the results.

High-modal gain 1300-nm In(Ga)As-GaAs quantum-dot lasers

A semiconductor laser containing seven InAs-InGaAs stacked quantum-dot (QD) layers was grown by molecular beam epitaxy. Shallow mesa ridge-waveguide lasers with stripe width of 120 mum were fabricated and tested. A high modal gain of 41 cm-1 was obtained at room temperature corresponding to a modal gain of ~6 cm-1 per QD layer, which is very promising to enable the realization of 1.3-mum ultrashort cavity devices such as vertical-cavity surface-emitting lasers. Ground state laser action was achieved for a 360-mum-cavity length with as-cleaved facets. The transparency current density per QD layer and internal quantum efficiency were 13 A/cm2 and 67%, respectively

Enhanced Performances of Quantum Dot Lasers Operating at 1.3

Due to their delta-like density of states, quantum dots (QDs) were expected to improve laser device performances with respect to quantum wells (QWs). Nevertheless, some important drawbacks limit this technology. For instance, QD laser still suffers from a low value of the modal gain, due to the low areal density of QDs, and inhomogeneous broadening, especially when multistacked layers are used. In this paper, we demonstrate that a linear increase of the QD modal gain with the QD layers number, as typically achieved in multi-QW lasers, is possible by a careful control of the Stranski-Krastanov QDs growth and QDs stacking optimization. A low-transparency current density of 10 A/cm2 per QD layer and a modal gain of 6 cm-1 per QD layer were achieved from laser structures containing up to seven QD layers. We demonstrate 10-Gb/s direct modulation (until a temperature of 50 degC) and high T 0 (110 K) from a single-mode device containing six QD layers.

\mu

High performance 1300 nm lasers based on self-organized InAs/InGaAs quantum dots (QDs) are reported. By optimizing the QD growth parameters and decreasing the waveguide thickness, a high modal gain and a low transparency current density of 32 cm−1 and 35 A cm−2, respectively, were obtained from a device containing five stacked QD layers. The internal quantum efficiency is as high as 90%.

m

In this letter, we report on experimental results of directly modulated single-transverse mode 1.3-mum InAs-InGaAs quantum-dot (QD) lasers in a wide temperature range. A 3.125-Gb/s data modulation over temperature with an extinction ratio up to 10 dB is reported. Moreover, 10-Gb/s eye patterns at 15 degC and 50 degC and 5-Gb/s modulation in the whole explored temperature range (15 degC-85 degC) are demonstrated. These results were obtained by exploiting heterostructures containing six layers of high modal gain InAs QDs grown without incorporation of p-doping in the active region or tunnelling injection structure implementation. QD lasers exhibited a saturation modal gain as high as 36.3 cm-1, ground state lasing from short cavities down to 400-mum length and a characteristic temperature of about 110 K in a large temperature range between 15 degC and 85 degC

High efficiency and high modal gain InAs/InGaAs/GaAs quantum dot lasers emitting at 1300 nm

We investigate the optical properties of light-emitting diodes (LEDs) operating at 1.3 μm embedding, in the intrinsic region, quantum dots (QDs) directly grown by metalorganic chemical-vapor deposition in a GaAs matrix, without indium in the barrier. The device characterization shows a full width at half maximum of the ground state emission as narrow as 24 meV at room temperature and a quenching of the emission between 30 K and room temperature as low as 2.75. Despite the low dot density (1.6×109 cm−2), the external quantum efficiency of our devices is 0.03%. This indicates that the individual QD efficiency of our devices is about 30% higher than that reported in the literature for state of the art InGaAs/InGaAs QD LEDs.

High-Performance Directly Modulated 1.3-

We present a quantum-dot microcavity light-emitting diode emitting at 1.3 μm at room temperature. The long wavelength emission is achieved by using InGaAs quantum dots directly grown on GaAs, by metalorganic chemical vapor deposition. The device exhibits electroluminescence bright emission, peaked at 1298 nm and with a full width at half maximum of 6.5 meV.

\mu

This paper presents a new AlN-based MEMS devices suitable for vibrational energy harvesting applications. Due to their particular shape and unlike traditional cantilever which efficiently harvest energy only if subjected to stimulus in the proper direction, the proposed devices have 3D generation capabilities solving the problem of device orientation and placement in real applications. Thanks to their particular shape, the realized devices present more than one fundamental resonance frequencies in a range comprised between 500 Hz and 1.5 kHz, with a voltage generation higher than 300μV and an output power up to 0.4 pW for single MEMS device.

m Undoped InAs–InGaAs Quantum-Dot Lasers

In-plane absorption measurements were performed at room temperature by means of a waveguide transmission setup on a Stranski–Krastanov InAs dots-in-a-well system emitting at 1.3μm embedded in a p-i-n structure. The polarization dependence of quantum dot (QD) absorption was exploited to resolve its discrete and continuous spectral components and study them separately under reverse bias application. The quantum confined Stark effect observed in the discrete spectral component gave evidence of an upward built-in QD dipole of about 9.5×10−29Cm. The continuous component was found to originate from electronic transitions involving a QD state and a quantum well state.

1.31 μm InGaAs quantum dot light-emitting diodes grown directly in a GaAs matrix by metalorganic chemical-vapor deposition

Herein we describe the realization of nanowalled polymeric microtubes through a novel and versatile approach combining the layer-by-layer (LbL) deposition technique, the self-rolling of hybrid polymer/semiconductor microtubes and the subsequent removal of the semiconductor template. The realized channels were characterized in detail using scanning electron and atomic force microscopes. Additionally, we report on the incorporation of a dye molecule within the nanowalls of such microtubes, demonstrating a distribution of the fluorescence signal throughout the whole channel volume. This approach offers the possibility to tailor the properties of micro/nanotubes in terms of size, wall thickness and composition, thus enabling their employment for several applications.