Propriedades ópticas de pontos quânticos semicondutores de InAs/GaAs

Abstract

Semiconductors quantum dots(QDs)have attracted considerable interest from both fundamental and technological point of view and have been extensively studied in aspects involving its structural properties and the electronic structure of the confined charge carriers. These systems have been utilized for applications in optoelectronics devices such as lasers, detectors, photodiodes, solar cells, etc. Quantum dots grown by Stranski-Krastanov (SK) technique are self-assembled islands, favored by relaxation of the elastic energy that emerge due to the difference of lattice parameter between the epitaxial layer and the substratum. One of the challenges in growing of QDs by SK is to have control of both size and distribution of the islands in the samples. Recently, the growth of samples with vertically stacked multilayer separated by a layer of another semiconductor material,known as stacked QDs, have shown a vertical alignment of QDs which leads to a better QDs size uniformization for the upper layers. In this work we have study a set of self-assembled InAs/GaAs double QDs grown on GaAs-(001)substrates by molecular beam epitaxy obtained by SK technique with GaAs spacer layers having different thickness, using photoluminescence technique as a function of excitation intensity at low temperature. PL spectra as a function of laser excitation intensity indicate that a bimodal behavior occurs in the reference sample. The PL results from stacked QDs can be explained by a competition between the effects of red-shift associated with the electronic coupling of the QDs in different layers, which is proportional to the thickness of the spacer layer, and of blue-shift associated with the In/Ga interdiffusion (intermixing), which occurs during the growth process.