Critical strain region evaluation of self-assembled semiconductor quantum dots

Abstract

A novel peak finding method to map the strain from high resolution transmission electron micrographs, known as the Peak Pairs method, has been applied to In(Ga)As/AlGaAs quantum dot (QD) samples, which present stacking faults emerging from the QD edges. Moreover, strain distribution has been simulated by the finite element method applying the elastic theory on a 3D QD model. The agreement existing between determined and simulated strain values reveals that these techniques are consistent enough to qualitatively characterize the strain distribution of nanostructured materials. The correct application of both methods allows the localization of critical strain zones in semiconductor QDs, predicting the nucleation of defects, and being a very useful tool for the design of semiconductor devices.

Exploring semiconductor quantum dots and wires by high resolution electron microscopy

“…The strain field obtained by applying strain mapping has been compared to that calculated by solving the anisotropic elastic theory equations by Finite Element Analysis (FEA), giving good agreement. In [21], the correct application of both methods has allowed the localization of critical strain zones in semiconductor In(Ga)As/AlGaAs quantum dot (QD) samples, predicting the nucleation of defects. In [22], experimental strain field maps of stacked nanostructures show a good correspondence with the strain values calculated by FEA.…”

“…The application of these approaches in combination with other analytical methods has allowed us to successfully predict the nucleation sites of stacked quantum wires for different growth conditions [18][19], learning about the nucleation mechanism of these nanostructures [20] and the defect nucleation mechanism in quantum dots [21]. Good correlation has been found in these nano-wires between the strain maps obtained directly from the strain analysis of HRTEM images and the strain calculated by finite element methods using the compositional maps determined by HAADF-STEM and electron energy-loss spectroscopy (EELS) [22].…”

Micro- and Nano-X-ray Beams

“…For the structural characterization of nanoscale objects, X-ray diffraction is widely used as a nondestructive technique, complementing and extending other local probe analysis methods such as SEM and TEM, which are intrinsically limited to investigations of surfaces, thinned, or cleaved samples [106,107]. With the development of increasingly miniaturized structures for technological applications in electronics and photonics, the use of local probes is becoming more and more relevant to obtain information at short length scales and thus to understand the properties related to the small size.…”

Nano‐beam electron diffraction evaluation of strain behaviour in nano‐scale patterned strained silicon‐on‐insulator

“…For analyzing the series of diffraction patterns a commercial software package was used which precisely determines the centers of the diffraction spots and the displacement of their positions in relation to reference patterns acquired in an unstrained area of the sample [17]. Beside the NBED technique the recently developed peak-pairs analysis was applied to HAADF images [12,18,19], which were acquired close to Gauss defocus by use of an illumination semi-convergence angle of 24 mrad and a detector collection angle of 50 mrad < 2θ < 200 mrad. The 1k or 2k images were taken in different specimen regions being adjusted in <110> zone axis orientation with a < 0 1 1 > direction of the strained silicon parallel to the scan lines.…”