Abstract
The 3D distribution of self-assembled stacked quantum dots (QDs) is a key parameter to obtain the highest performance in a variety of optoelectronic devices. In this work, we have measured this distribution in 3D using a combined procedure of needle-shaped specimen preparation and electron tomography. We show that conventional 2D measurements of the distribution of QDs are not reliable, and only 3D analysis allows an accurate correlation between the growth design and the structural characteristics.
Highlights
Most optoelectronic devices based in quantum dots (QDs) such as optical amplifiers [1], infrared detectors [2], or lasers [3] require stacking of multiple QDs layers to enhance properties as the number of photons emitted or absorbed per unit area
The Indium arsenide (InAs) QDs can be clearly observed as they exhibit brighter contrast than the Gallium arsenide (GaAs) matrix because of the higher average Z number
Because of the rounded shape of the QDs, they are not expected to show sharp upper interfaces when observed by highangle annular dark field (HAADF) but with diffused boundaries, in which the contrast is gradually reduced at the edge, as it is shown in the image
Summary
Most optoelectronic devices based in quantum dots (QDs) such as optical amplifiers [1], infrared detectors [2], or lasers [3] require stacking of multiple QDs layers to enhance properties as the number of photons emitted or absorbed per unit area. QDs tend to align vertically because of the strain fields caused by the buried dots [4,5]. These strain fields have a strong effect in the size and shape of the QDs and in the optoelectronic properties of the corresponding devices [6,7,8,9,10,11]. The vertical distribution of the QDs has a direct effect in its electronic structure due to a possible electron tunneling between layers [12], and it has been found to influence optical properties such as the photoluminescence emission of the structure [13]. Various techniques have been used to assess the vertical distribution of QDs [14,15,16], one of the most
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