Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 7 de 7
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Nanoscale ; 11(45): 21847-21855, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31696191

RESUMO

Realizing single photon sources emitting in the telecom band on silicon substrates is essential to reach complementary-metal-oxide-semiconductor (CMOS) compatible devices that secure communications over long distances. In this work, we propose the monolithic growth of needlelike tapered InAs/InP quantum dot-nanowires (QD-NWs) on silicon substrates with a small taper angle and a nanowire diameter tailored to support a single mode waveguide. Such a NW geometry is obtained by a controlled balance over axial and radial growths during the gold-catalyzed growth of the NWs by molecular beam epitaxy. This allows us to investigate the impact of the taper angle on the emission properties of a single InAs/InP QD-NW. At room temperature, a Gaussian far-field emission profile in the telecom O-band with a beam divergence angle θ = 30° is demonstrated using a single InAs QD embedded in a 2° tapered InP NW. Moreover, single photon emission is observed at cryogenic temperature for an off-resonant excitation and the best result, g2(0) = 0.05, is obtained for a 7° tapered NW. This all-encompassing study paves the way for the monolithic growth on silicon of an efficient single photon source in the telecom band based on InAs/InP QD-NWs.

2.
Nanoscale ; 10(43): 20207-20217, 2018 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-30357204

RESUMO

One obstacle for the development of nanowire (NW) solar cells is the challenge to assess and control their nanoscale electrical properties. In this work a top-cell made of p-n GaAs core/shell NWs grown on a Si(111) substrate by Molecular Beam Epitaxy (MBE) is investigated by high resolution charge collection microscopy. Electron Beam Induced Current (EBIC) analyses of single NWs have validated the formation of a homogeneous radial p-n junction over the entire length of the NWs. The radial geometry leads to an increase of the junction area by 38 times with respect to the NW footprint. The interface between the NWs and the Si(111) substrate does not show any electrical loss, which would have led to a decrease of the EBIC signal. Single NW I-V characteristics present a diodic behavior. A model of the radial junction single NW is proposed and the electrical parameters are estimated by numerical fitting of the I-Vs and of the EBIC map. Solar cells based on NW arrays were fabricated and analyzed by EBIC microscopy, which evidenced the presence of a Schottky barrier at the NW/ITO top contact. Improvement of the top contact quality is achieved by thermal annealing at 400 °C, which strongly reduces the parasitic Schottky barrier.

3.
Nano Lett ; 16(5): 2926-30, 2016 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-27046672

RESUMO

The elastic properties of InP nanowires are investigated by photoluminescence measurements under hydrostatic pressure at room temperature and experimentally deduced values of the linear pressure coefficients are obtained. The pressure-induced energy shift of the A and B transitions yields a linear pressure coefficient of αA = 88.2 ± 0.5 meV/GPa and αB = 89.3 ± 0.5 meV/GPa with a small sublinear term of ßA = ßB = -2.7 ± 0.2 meV/GPa(2). Effective hydrostatic deformation potentials of -6.12 ± 0.04 and -6.2 ± 0.04 eV are derived from the results for the A and B transitions, respectively. A decrease of the integrated intensity is observed above 0.5 GPa and is interpreted as a carrier transfer from the first to the second conduction band of the wurtzite InP.

4.
Nanotechnology ; 26(39): 395701, 2015 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-26349621

RESUMO

The emission polarization of single InAs/InP quantum dot (QD) and quantum rod (QR) nanowires is investigated at room temperature. Whereas the emission of the QRs is mainly polarized parallel to the nanowire axis, the opposite behavior is observed for the QDs. These optical properties can be explained by a combination of dielectric effects related to the nanowire geometry and to the configuration of the valence band in the nanostructure. A theoretical model and finite difference in time domain calculations are presented to describe the impact of the nanowire and the surroundings on the optical properties of the emitter. Using this model, the intrinsic degree of linear polarization of the two types of emitters is extracted. The strong polarization anisotropies indicate a valence band mixing in the QRs but not in the QDs.

5.
Opt Express ; 22(12): 14830-9, 2014 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-24977578

RESUMO

We present the mechanisms underlying the redshifted and blueshifted photoluminescence (PL) of quantum dots (QDs) upon amorphization of phase change material (PCM). We calculated the stress and energy shift distribution induced by volume expansion using finite element method. Simulation result reveals that redshift is obtained beneath the flat part of amorphous mark, while blueshift is obtained beneath the edge region of amorphous mark. Simulation result is accompanied by two experimental studies; two-dimensional PL intensity mapping of InAs/InP QD sample deposited by a layer of PCM, and an analysis on the relationship between PL intensity ratio and energy shift were performed.

6.
Opt Express ; 17(7): 5439-45, 2009 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-19333310

RESUMO

We have designed, fabricated, and characterized an InP photonic crystal slab structure that supports a cavity-confined slow-light mode, i.e. a bandgap-confined valence band-edge mode. Three dimensional finite difference in time domain calculations predict that this type of structure can support electromagnetic modes with large quality factors and small mode volumes. Moreover these modes are robust with respect to fabrication imperfections. In this paper, we demonstrate room-temperature laser operation at 1.5 mum of a cavity-confined slow-light mode under pulsed excitation. The gain medium is a single layer of InAs/InP quantum dots. An effective peak pump power threshold of 80 microW is reported.


Assuntos
Arsenicais/química , Índio/química , Lasers , Fosfinas/química , Pontos Quânticos , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Miniaturização , Fótons , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Temperatura
7.
Opt Express ; 14(20): 9269-76, 2006 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-19529309

RESUMO

The authors report on the design, fabrication and operation of heterogeneous and compact "2.5 D" Photonic Crystal microlaser with a single plane of InAs quantum dots as gain medium. The high quality factor photonic structures are tailored for vertical emission. The devices consist of a top two-dimensional InP Photonic Crystal Slab, a SiO(2) bonding layer, and a bottom high index contrast Si/SiO(2) Bragg mirror deposited on a Si wafer. Despite the fact that no more than about 5% of the quantum dots distribution effectively contribute to the modal gain, room-temperature lasing operation, around 1.5 microm, was achieved by photopumping. A low effective threshold, on the order of 350 microW, and a spontaneous emission factor, over 0.13, could be deduced from experiments.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA