A Comprehensive Study and Modeling Approach for static and Dynamic Characteristics of vertical GaN Devices

In the rapidly evolving field of wide-bandgap semiconductors, vertical GaN devices stand out for their potential to revolutionize high-power and high-frequency applications. Various structures for GaN vertical devices such as current aperture vertical electron transistors (CAVET), trench MOSFETs, Vertical Fin FET, and Vertical JFET have been fabricated. The GaN CAVET structure combines the benefits of both horizontal and vertical topologies. The CAVET has exceptional performance in fast-switching power conversion applications. The higher switching frequency of CAVET contributes to reduced passive component size, thereby decreasing device cost. This talk will dive into a detailed exploration of the static and dynamic performance of vertical GaN devices, focusing on key parameters such as threshold voltage stability, breakdown voltage, and transconductance. By bridging experimental data with advanced modeling techniques, this lecture offers new insights into optimizing device performance under varying operational conditions.

Main advantage of nitrides over SiC: posibility to grow heterostructures

In last years a lot of attention of both, research and industry, was devoted to wide band gap materials such as GaN, SiC or Ga2O3. Each of this material will have preferred field of application. GaN is the best candidate in case that the combination of high frequency and high power is required. Beside outstanding material properties, such as high breakdown voltage, high electron velocity and good thermal conductivity GaN has one crucial advantage – possibility to grow heterostructures (combination of layers with different composition and properties) in combination with polar wurtzite crystal structure with strong polarization electric field near interfaces. Thanks to this, AlGaN/GaN heterointerface forms quantum well (QW) with 2D electron channel with high electron concentration, which shields the electric field around ionized impurities and considerably decreases electron scattering on them. The talk will show experiences with different architecture of d-HEMT and e-HEMT structures – influence of back barriers, dislocation density, interface morphology or dielectric deposition and photolithography of transistor structures obtained in FZU during last few years.

Optical properties of SiC

Electromagnetic response at optical frequencies, crystal structure & optical anisotropy, lattice vibrations and free carriers at low frequencies/photon energies (<ė 100 THz / 0.4 eV), low-energy excitations using Raman scattering, interband electronic transitions at high frequencies/photon energies (>ė 0.8 PHz / 3.2 eV), “transparent” range in between, inter-conduction electronic transitions in heavily doped n-type. Optical spectroscopy as diagnostic tools, exposition to focused laser beam - wafering.

Structural properties of wide band gap semiconductors

Structure of wide gap semiconductors SiC, GaN, (Al,Ga)N, Ga2O3 a their polymorphs. Common defect types in WBG semiconductors. Methods for defect analysis in semiconductors using x-ray scattering techniques. Visualisation of defects and strain using x-ray diffractometric techniques and imaging in polariyed light. Strain and strain induced defects in epitaxial films and nanostructures.

Applications of Electron Microscopy and Adjacent Techniques is Failure Analysis of Wide Band Gap Semiconductors

Wide Band Gap (WBG) semiconductors have unique set of physical and electrical properties, which are often highlighted. In reality leveraging these properties creates a unique set of challenges to tackle
(i.e. crystalline defectivity, doping control, heat management, ...) in order to exploit WBG semiconductors' full potential over various applications. Electron microscopy always played vital role in structural, dimensional, material or chemical analysis of semiconductors. Challenges tied to WBG create novel requirements for Failure Analysis technology vendors in order to provide instrumentation capable of providing relevant information in timely manner. In this talk we will explore the challenges behind WBG Failure Analysis workflows and project it into requirements and possible solutions how to manage FA of WBG.

Fundamentals and Recent Advances in SiC Epitaxy

This lecture focuses on the epitaxy process of silicon carbide (SiC), a key material for manufacturing efficient semiconductor devices used in demanding power switching applications. We will introduce the basic principles and challenges of SiC epitaxy, along with the existing hot-wall chemical vapor deposition (CVD) epitaxial reactors. A critical aspect in the industrial environment is the characterization and control of critical parameters of SiC epitaxial layers: thickness, doping, and defectivity. Established characterization methods will be presented, and recent technological advances will be highlighted. Finally, we will summarize the challenges for the near future.

Get in touch with SiC wafers

Experiments and practical training on SiC and Si wafers. Demonstration of their optical properties. Instrumentation for structure analysis and device processing. Visit to the laboratories and the clean room semiconductor facility at the Department of Condensed Matter Physics.