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11. Enhanced Performances of Quantum Dot Lasers Operating at 1.3 \mu m.

Author

Salhi, A., Raino, G., Fortunato, L., Tasco, V., Visimberga, G., Martiradonna, L., Todaro, M.T., De Giorgi, M., Cingolani, R., Trampert, A., De Vittorio, M., and Passaseo, A.

Abstract

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. [ABSTRACT FROM PUBLISHER]

Published
2008
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13. High-modal gain 1300-nm In(Ga)As-GaAs quantum-dot lasers.

Author

Salhi, A., Martiradonna, L., Visimberga, G., Tasco, V., Fortunato, L., Todaro, M.T., Cingolani, R., Passaseo, A., and De Vittorio, M.

Abstract

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 [ABSTRACT FROM PUBLISHER]

Published
2006
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17. High-k YCTO thin films for electronics

Author

Elisabetta Mazzotta, Indira Chaitanya Lekshmi, Abhijit Hazarika, Debraj Choudhury, Maurizio Martino, Anna Paola Caricato, Giuseppe Maruccio, D. D. Sarma, Cosimino Malitesta, Vittorianna Tasco, Zoobia Ameer, Silvia Rizzato, Angelo Leo, Anna Grazia Monteduro, Monteduro, A. G., Ameer, Z., Rizzato, S., Leo, A., Martino, M., Caricato, A. P., Tasco, V., Lekshmi, I. C., Hazarika, A., Choudhury, D., Mazzotta, E., Malitesta, C., Sarma, D. D., and Maruccio, G.

Subjects
Permittivity, Materials science, 02 engineering and technology, Substrate (electronics), Dielectric, rare-earth copper titanate, dielectric characterization, 01 natural sciences, MOS capacitor, Gate oxide, 0103 physical sciences, universal dielectric response, Thin film, dielectric, High-κ dielectric, 010302 applied physics, business.industry, high-k material, 021001 nanoscience & nanotechnology, Microstructure, Titanate, Maxwell-Wagner effect, amorphous oxides thin film, Optoelectronics, 0210 nano-technology, business
Abstract

The high permittivity values reported in rare-earth transition metal oxides ceramics makes them very interesting as alternative gate dielectrics. Here, we summarize our recent results on the yttrium copper titanate (YCTO) thin films under different deposition conditions. Their dielectric properties were studied both in metal-oxide-metal (MIM) and in metal-oxide-semiconductor (MOS) junctions for respectively investigating the material response without parasitic substrate contributions and evaluating the YCTO performance as gate oxide. A strongly dependence of the permittivity from deposition conditions was observed, with a variation from 100 down to 24 at 100 kHz. Such behavior was ascribed to film microstructure variations. Notably, at certain deposition conditions, YCTO thin films possess a higher dielectric permittivity than their bulk counterpart (40.3) in addition to good performances in term of losses. These results demonstrate the applicability of YCTO as alternative high-k gate oxides.

Published
2018
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18. High Gain 1300 nm Quantum Dot Lasers

Author

Vittorianna Tasco, Abdelmajid Salhi, Maria Teresa Todaro, Adriana Passaseo, M. De Vittorio, Laura Fortunato, Passaseo A., Salhi A., Todaro, M. T., Fortunato, L., Tasco, V., and DE VITTORIO, Massimo

Subjects
Range (particle radiation), Materials science, business.industry, Atmospheric temperature range, Laser, law.invention, Transverse mode, Gallium arsenide, chemistry.chemical_compound, Optics, chemistry, law, Modulation, Quantum dot laser, Optoelectronics, business, Current density
Abstract

In this work, we show that a modal gain as high as 42cm-1 could be achieved from a device containing 7 InAs/InGaAs stacked QD layers. The enhancement of the modal gain is accompanied by a decrease of the threshold and transparency current densities per QD layer down to 16 and 7 A cm-2, respectively. Moreover, a linear increase of the modal gain with the number of QD layers is observed. The obtained high modal gain allows us to achieve good temperature stability and high-speed operation in a wide temperature range. Modulation eye diagrams under 10 Gb/s are achieved in 15degC-50degC range in a single- transverse mode 1.3mum QD lasers. High characteristic temperature of about 110 K between 15degC and 85degC are reported.

Published
2007
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