Investigação da Difusão de Portadores em Pontos Quânticos Sob Campo Elétrico Externo Por Meio da Varredura da Microluminescência

AUTOR(ES)

Flávio Augusto de Melo Marques

DATA DE PUBLICAÇÃO

2009

RESUMO

In this work, we present the study of energy transfer processes between self-assembled quantum dots (QDs) of InAs in GaAs layers within an intrinsic region of a p-i-n device. These p-i-n structures are assembled with electrical contacts providing the application of an electrical potential. The three samples used have diferent layer spacing and barrier size between the quantum dots (QDs). The main investigation was performed by means of the spectrally and spatially resolved micro-photoluminescence (PL) as a function of the perpendicular electrical field, excitation intensity and recombination energy. From the PL spectra five emission peaks were observed in association with the difierent energy states of the QDs. For each energy state the PL scan was used to identify the energy transfer between the QDs. We found evidence that the energy transfer between the QDs is larger at the lower energy states, and that by decreasing the electrical field within the intrinsic region it may induce the increase of the energy transfer for each QD energy state. These energy transfer processes have been associated with the carrier difusion within the barrier, together with another process such as thermal activation. We have also carried out spatially resolved PL as a function of the emission wavelengths. The energy transfer between QDs decreases linearly with the electron-hole recombination energy. From this result we conclude that the energy transfer phenomenon occurs onto a Gaussian distribution of diusing carriers, in which the concentrations of electrons-hole pairs reaching longer distances are smaller, just enough to fill the lower energy states from QDs. Finally, state filling efects of the QDs have been observed from the PL measurements as function of excitation energy.

ASSUNTO(S)

transferência de energia fisica fotoluminescência microluminescence microluminescência energy transfer semiconductors semicondutores energia - transferência electric field pontos quânticos matéria condensada quantum dots photoluminescence campo elétrico

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