Institute of High Pressure Physics of the Polish Academy of Sciences

Abstract1:

AlGaInN and BN compounds are the second (after Si) important group of semiconductors, taking into account the market size. The largest application is the production of white LEDs; the others include laser diodes for projectors or copper welding, as well as transistors operating at high frequencies and powers. In the first part of the presentation, those and other future applications will be reviewed. Nitride semiconductors are much more difficult to grow and process as compared with other semiconductors as Si, Ge, GaAs, InP, or SiC. The main problem is related to the substrates. All LEDs and transistors are fabricated on foreign substrates (sapphire or Si), which are highly lattice-mismatched. Laser diodes are fabricated on bulk GaN substrates, which are still small and expensive. The second part of the presentation will be devoted to that issue, showing the advantages of ammonothermal bulk GaN substrates grown in the IHPP.

The dislocations and other extended defects are present in nitrides at much higher densities than in other semiconductors; however, even more serious problems are point defects: vacancies and impurities. They migrate very easily. This will be shown in two examples:

i) Homogenization and decomposition of the InGaN QWs,

ii) Diffusion of Mg and Si.

Abstract 2:

The thermal stability of green light-emitting quantum wells (QWs) is a critical factor influencing the performance and longevity of optoelectronic devices. This study investigates the impact of metal-organic vapor phase epitaxy (MOVPE) growth parameters—such as temperature, V/III ratio, and growth rate—on the structural and optical stability of InGaN/GaN QWs emitting in the green spectral range. Samples containing green QWs were studied using photoluminescence (PL), high-resolution X-ray diffraction (HR-XRD) and scanning/transmission electron microscopy (SEM/TEM).

Abstract 3:

In this work, we present a theoretical study on the formation and thermodynamic stability of native point defects in gallium nitride (GaN) grown by Metal-Organic Chemical Vapor Deposition (MOCVD). Using density functional theory (DFT), we model the energetics and configurations of isolated vacancies and vacancy complexes, focusing particularly on VGa, VN, and their combinations with oxygen and hydrogen. To accurately capture defect thermodynamics under realistic growth and annealing conditions, we incorporate vibrational contributions through first-principles phonon calculations. These time-consuming simulations, carried out within the harmonic approximation, provide access to zero-point energies and temperature-dependent vibrational free energies, revealing nontrivial temperature effects on defect formation energies.

Abstract 4:

In order to increase degree of freedom in designing new devices and achieve new functionalities much effort is recently concentrated on controlled growth of GaN nanowires on non-conventional substrates, including non-crystalline materials. In this talk I will focus on an influence of a substrate on self-induced nucleation and growth as well as on properties of GaN nanowires on non-crystalline substrates. As example, a comprehensive description of the self-assembled nucleation and growth of GaN nanowires by MBE on amorphous AlxOy buffers will be presented and compared with analogous processes occurring under otherwise identical growth conditions on nitridated Si – the substrate commonly used for MBE growth of GaN nanowires. In this way, a general understanding of the formation of GaN nanowires is sought, with particular emphasis on the role of the substrate and its influence on the growth process.

Abstract 5:

There is increasing interest in growing GaN nanowires on metal substrates. Metal buffer layers show high electrical and thermal conductivities and optical reflectivity, and provide both a nucleation layer for growth and potentially offer a backside electrical contact for bottom-up optoelectronic structures. In the talk I will show that well-oriented device-relevant GaN nanowire arrays on Si or sapphire substrates with metallic ZrN buffer layers can be fabricated by plasma-assisted MBE. Kelvin probe and TEM measurements show perfect nitrogen-polarity of the nanowires without any sign of mixed polarity commonly observed for self-assembled GaN nanowires on Si. Electrical measurements show a low resistive ohmic electrical contact of ZrN to bottom parts of the nanowires, so the ZrN buffer can play a role of buried electrical contact allowing efficient controlling electrically-driven light emitters based on GaN nanowires. Moreover, a good rectifying characteristic of p-n junction inside a single nanowire is observed.

Brief CV of Prof. Mike Leszczynski：

Author of more than 400 papers on semiconductors, H-factor 45. Head of the Laboratory of Semiconductor Microstructure. Vice-president of TopGaN Lasers. President of the Polish Society of Crystal Growth.

Brief CV of Dr. Robert Czernecki：

Author of about 100 papers on nitride semiconductors, H-factor 25. Head of MOVPE Lab.

Brief CV of Dr. Roman Hrytsak：

Research interests lie at the interface of computational modeling and III-V semiconductors. Dedicated to employing crystal growth simulations to understand epitaxial growth processes, focusing on optimizing techniques like MOVPE and MBE. Through ab initio calculations, delve into the thermodynamics and surface physics of these materials, uncovering their electronic structure and surface properties.

Brief CV of Prof. Zbigniew R. Zytkiewicz：

Full professor at the Institute of Physics Polish Academy of Sciences, chairman of the Crystalline Microstructures Section of the Polish Society for Crystal Growth; his research focuses on physics and technology of epitaxial growth of III-V semiconductors, in the past by liquid phase epitaxy and epitaxial lateral overgrowth, currently by MBE.

Brief CV of Prof. Marta Sobanska：

Professor at the Institute of Physics Polish Academy of Sciences, head of Laboratory for MBE growth of nitride nanostructures at IP PAS. Her research concerns epitaxial growth of group III nitride nanostructures and advanced studies of their properties.

腾讯会议ID：330-627-974

会议密码：0811

主持人：王刚 研究员

联系人：傅琦 （82649469）