Conference Agenda

The incorporation of Bi into GaAs has demonstrated significant potential for reducing excess noise in avalanche photodiodes (APDs) by lowering the hole ionization coefficient. It has been proposed that the incorporation of group III elements in GaAsBi alloys, such as Al, could facilitate the development of a novel class of ultra-low noise APDs utilizing GaAs substrates. This study investigates the growth dynamics, surface morphology, and optical properties of AlGaAsBi alloys epitaxially grown on GaAs substrates. By systematically varying the Bi flux and III/V ratio, we identify two distinct types of superficial nanomotifs: "caldera volcanoes" and "dome volcanoes," associated with Bi-rich and Ga-Al-Bi droplets, respectively. The results reveal that higher Bi flux improves interface quality but can lead to droplet formation, while the presence of Al modifies droplet dynamics. These findings provide critical insights into optimizing AlGaAsBi growth for low-noise APDs operating in the near-infrared range.

The results of a throughout investigation of β‐Ga2O3/4H-SiC heterostructures are presented, with particular attention to the nucleation of Ga2O3 islands on the stepped 4H-SiC surface. The formation of domains resulting from the deposition of a monoclinic material on a hexagonal substrate is also presented and discussed. This study opens new perspectives for the preparation of heterostructures with improved properties.

Opposite to planar heterostructures, nanowires (NWs) allow heterostructures to overcome the limits regarding lattice mismatch and strain relief. However, the structural characterization of heterostructured NWs is typically done by means of transmission electron microscopy (TEM), costly and time consuming. In this work, an angular multi-segment detector in backscatter electron (BSE) configuration is employed to analyse III/V semiconductor NWs. We analyse three different sets of NWs: 1.- InGaN/GaN; 2.- GaInP/InP based tandem solar cells; and 3.- triangular GaAs/InAs core/shell. First, we carry out a comprehensive study of the beam conditions (acceleration voltage and beam current) to achieve the highest contrast between the core and the shell. In this work, we demonstrate that by properly adjusting contrast and brightness, either the topography or the compositional contrast can be enhanced. Finally, we show preliminary results in the characterization of defects such as stacking faults and twin-plane superlattices in axially heterostructured NWs.

ULTRARAM is a low-voltage, ultrafast memory that merges the speed of dynamic random-access memory (DRAM) with the data retention capabilities of a flash memory. The performance of the device relies on a triple barrier resonant tunneling (TBRT) structure, based on a InAs/AlSb heterostructure. Hoever, achieving atomically sharp interfaces within this structure poses a significant challenge due to unintended atomic intermixing and segregation. This lead to the formation of the quaternary alloy Al(x)In(1-x)As(y)Sb(1-y) near the interfaces, that could expand to most of the layer.

In this study, we quantitatively analyze atomic-resolution annular dark field (ADF) scanning transmission electron microscopy (STEM) images by comparing experimental ADF-STEM intensities with image simulations of the quaternary alloy. This analysis is completed by atomic-resolution energy dispersive X-ray (EDX) spectroscopy maps, providing a comprehensive understanding of elemental distribution and interface quality. The resulting Sb composition is modeled using Muraki's segregation model.

The semiconductor sector has an important need of characterization of materials, in particular, crystalline defects that can be detrimental for devices performance. To this aim, electron channelling contrast imaging (ECCI) has emerged as fast and a non-destructive technique for defect characterization. In this work we established a protocol to easily achieve ECCI measurement conditions in a scanning electron microscope (SEM). By using a retractable back scattered electron detector, we achieve direct observation of dislocation without any sample preparation and with small tilt angles. We have applied it for the characterization of Ga(In)As and GaSb thin films grown on Si. We study different measurement conditions to optimize the observation of defects. We demonstrate direct observation of threading and misfit dislocations in thin films while reducing preparation time, cost and labour compared to other characterization techniques such as transmission electron microscopy (TEM).