Strain Engineering in Semiconductor Materials

This Special Section on Strain Engineering in Semiconductor Materials guest-edited by Costanza Lucia Manganelli, Davide Spirito, Patricio Farrell, Jacopo Frigerio, Andrea De Iacovo, Damiano Marian, and Michele Virgilio highlights the potential of strain engineering in diverse contexts, offering both practical methodologies and profound theoretical insights. Strain engineering has become an essential strategy in the advancement of semiconductor technologies, providing a powerful mean to modulate the electronic, optical, and mechanical properties of materials. By introducing controlled deformation into crystal lattices, this approach enables enhanced carrier mobility, tailored bandgap energies, and improved device performance across applications in photonics, optoelectronics, and quantum technologies. This Special Section highlights the potential of strain engineering in diverse contexts, offering both practical methodologies and profound theoretical insights. Article 202400220 explores a compact, cost-effective, and non-destructive approach that leverages on the bulk photovoltage effect to probe non-uniform strain fields with an electrical measurement, using a benchmark device with silicon nitride stripes deposited under varying pressure conditions on germanium. The surface strains are assessed by Raman spectroscopy and finite element method simulations that integrates mechanical models with deformation potential theory to estimate the band edge energy landscape. Benchmarking experimental measurements against theoretical description of semiconductor properties related to defects, doping, and deformation, the study provides a proof of concept toward the development of a novel technique to probe the strain field, and at the same time offers valuable insights into strain-induced behavior in semiconductor materials. In the realm of metal–oxide–semiconductor (MOS) technologies, 202400221 sheds light on the effects of strain on leakage currents, an aspect often neglected despite its role in boosting performance of transistors. Experimental data combined with ab initio calculations reveal that strain strongly influences leakage currents via band-to-band tunneling and trap-assisted tunneling mechanisms. The research highlights that, in certain conditions, mechanical deformations are predicted to increase leakage currents by up to 150 times. These findings emphasize the dual nature of strain, whose effects may be detrimental for conventional inversion-mode MOS field-effect transistors (FETs) while their accurate control can enhance the performance of tunnel FETs, acting on band-to-band tunneling rate which defines the on-state current. Thus, the understanding of strain effects on leakage current opens pathways for optimizing semiconductor device reliability and efficiency. The exploration of transition metal dichalcogenides (TMDCs) in article 202400276 underscores the importance of strain engineering also in the context of flexible electronics. The authors of 202400276 show that the lattice distortion in heterostructures composed of layered TMDCs, such as MoTe2/WSe2 bilayers, significantly alters their electronic and optical properties. Their first-principle study employing density functional theory and many-body perturbation theory demonstrates that biaxial strain can transform the band alignment of these heterostructures from a type I to a type II configuration, enabling charge separation and improving optoelectronic functionality. Notably, when the lattice constant of WSe2 is expanded by 3.2% or more, the system undergoes an indirect-to-direct bandgap transition, accompanied by a consistent shift in energy of the first dark excitation. Importantly, the absorption onset remains stable under strain, preserving the fundamental optical properties of the material. These findings highlight strain as a precise tool for tuning the electronic and optical characteristics of TMDC heterostructures, paving the way for advanced applications in light-emitting devices and quantum systems. In the context of InGaN-based micro-light-emitting diodes, efficient red light emission can be achieved at high Indium content. In article 202400241 it is shown that strain engineering can be used to overcome the obstacles related to the low miscibility of InN in GaN due to the large lattice deformation experienced by this epilayer. To reduce the strain field, the authors demonstrate that strain relaxation is facilitated through the introduction of patterned InGaN pseudosubstrates on GaN-on-sapphire layers. By synchrotron-based scanning X-ray diffraction microscopy, researchers mapped lattice strain and tilt with nanoscale resolution, validating the effectiveness of their approach in enhancing Indium incorporation and also ensuring the production of high-quality, partially relaxed substrates. Such advancements are crucial for the development of high-resolution, energy-efficient displays for virtual and augmented reality, showcasing the practical impact of strain engineering in next-generation display technologies. In conclusion, all these studies illustrate the diverse applications and profound implications of strain engineering in semiconductor and device physics. By combining experimental innovations with theoretical modeling, current research is unlocking new possibilities for device performance optimization and material characterization across a broad spectrum of applications, from photonics and optoelectronics to sensing, lasing, quantum computing and beyond, redefining the capabilities of semiconductor technologies. Costanza Lucia Manganelli is a staff scientist at the Material Research Department of IHP – Leibniz-Institut für innovative Mikroelektronik (IHP) in Frankfurt (Oder), specializing in modeling and investigation of innovative semiconductor devices. From 2017 she holds a Ph.D. in Emerging Digital Technologies from Scuola Superiore Sant’Anna (Italy). Her work primarily revolves around modeling electrical, mechanical, thermal and optical properties of semiconductor materials and devices, for opto-electronics, sensing and quantum computing applications. Davide Spirito is a Ramon y Cajal research fellow at BCMaterials (Basque Center for Materials, Applications and Nanostructures, Leioa, Spain), where he studies innovative materials for energy harvesting. His research interests include applied optoelectronics, thermoelectrics and sensing, with a focus on studying materials properties and experimental techniques, such as electrical and optical characterization, and Raman spectroscopy. He obtained a Ph.D. in Condensed Matter Physics at Roma Tre University in 2012. Patricio Farrell leads the “Numerical Methods for Innovative Semiconductor Devices” research group at the Weierstrass Institute Berlin (WIAS). A mathematician specializing in numerical methods for science and engineering, his research focuses on numerical solutions for partial differential equations in semiconductor applications, spanning from charge transport models and strain in semiconductor heterostructures to atomistic coupling. He holds a Ph.D. from the University of Oxford and a habilitation from Freie Universität Berlin. Jacopo Frigerio is an Associate Professor of Physics at Politecnico di Milano. From 2014 he holds a Ph.D. in Physics from the same institution. His research focuses on the physics and applications of silicon-germanium heterostructures, especially for near and mid-infrared photonics. His expertise ranges from material growth to fabrication and characterization of photonic devices. Andrea De Iacovo is an Assistant Professor at Roma Tre University in the Department of Engineering, specializing in optoelectronics and photonics. He earned his Ph.D. for his studies of Schottky barrier thin-film transistors on polycrystalline silicon. Later, his research focused on the integration of novel materials for optoelectronics on a silicon platform. His current work includes developing advanced photodetectors for Ge-on-Si and quantum dot technology, particularly used in near-infrared and visible-blind sensors for applications like fire detection and air quality monitoring. His expertise ranges from the design and simulation of optoelectronic devices to their characterization. Damiano Marian is an Assistant Professor of Theoretical Condensed Matter Physics at the University of Pisa. He earned his Ph.D. in Physics from the University of Genoa in 2015 and has been a postdoctoral researcher at both the Autonomous University of Barcelona, Spain and the University of Pisa. His research focuses on transport properties in nanoelectronic devices, particularly 2D materials and their heterostructures, exploring spin and valley degrees of freedom, as well as flexible electronics. He employs multiscale simulation approaches, ranging from ab-initio methods to device-level current-voltage analysis. Michele Virgilio is an Associate Professor of Theoretical Condensed Matter Physics at Pisa University where he also received a Ph.D. in Physics in 2008. His research activities are devoted to the theoretical investigation of electronic, spin, and optical properties of group IV semiconductor micro and nanostructures, mainly targeting photonic applications. His investigations have led to relevant advances for the development of CMOS compatible optical amplifiers based on Silicon/Germanium heterostructures operating in the near-infrared and THz spectral regions.