Using TCAD To Simulate Wide-Bandgap Materials For Electronics Design

Wide-bandgap (WBG) semiconductors are a class of materials that can offer a range of advantages over silicon. These materials can operate at higher voltages and higher temperatures, serving as critical enablers of innovation in Power and RF applications and functioning in a wider range of environments that are sometimes extreme. Electronics applications benefit from these wide-bandgap materials by allowing for the design of components that are faster, smaller, more efficient, and more reliable.

How are WBG materials useful?

Two prominent WBG semiconductor material in use today are gallium nitride (GaN) and silicon carbide (SiC). These materials are both able to withstand higher electric fields and high temperatures, making them particularly attractive in power electronics applications especially for the design of inverters, power supplies, and motor drives. Automotive applications such as electric vehicles (EVs) and plug-in hybrid EVs benefit from the characteristics that GaN and SiC can bring to power devices. In addition, GaN is also an important material in high-frequency devices like RF amplifiers and has led to improvements in wireless communication and 5G networks.

Accounting for the physics and chemistry of WBG materials in TCAD

Of course, many aspects of developing GaN and SiC for use in the semiconductor industry are more complex, and this is especially true in the field of Technology Computer Aided Design (TCAD). Traditionally, TCAD has relied on calibration to create accurate models and the model parameter to reproduce experimental measurements. Since the predominant material has been Si, millions of experiments have been conducted over the years that are continually used and updated to make sure TCAD simulations are correct. Adopting new materials means calibrating the physical parameters, which often leads to the need to create new models because materials like GaN have much different physics than Si that governs their behavior. For example, GaN can experience spontaneous polarization due the nitride atoms and can impact how atoms diffuse through the crystal structure.

Synopsys has invested in the development of a dedicated calibration tool, Sentaurus Calibration Workbench (SCW), that utilizes machine learning AI technology to automate the calibration of materials properties. SCW is positioned to calibrate the entire suite of Sentaurus TCAD tools for a wide range of applications.

Calibration requires data to calibrate to. Experimental data is preferred whenever possible, but this data often doesn’t exist, especially for new materials with novel new physics.

Synopsys often collaborates with industry partners or academia to develop accurate parameters for GaN and SiC for Power and RF applications. These collaborations advanced the accuracy of our TCAD tools by providing direct calibration to experimental data. It is interesting to keep in mind that experimental measurement techniques are also advancing and the parameters available now can be more accurate than they were a few years ago, making TCAD even more accurate.

Another aspect of GaN’s unique properties is that it shows a high level of variability in experimental data. This means that even when measurements can be made, precise knowledge of the data is not possible, and a range of values are possible. When experimental data isn’t available, engineers look to more physically accurate simulation tools for model calibration.

The next era of materials simulations

For design teams planning product development based on GaN and SiC, one of the biggest considerations is how to mitigate impurities. Synopsys supports this challenging but exciting journey of discovery with Synopsys QuantumATK atomic-scale modelling software, which allows for highly realistic materials simulations. While advanced, the process is less of a departure from traditional material simulation than one might imagine. A ‘principles first’ approach means we can simulate any fundamental material and its properties, then calibrate our TCAD tools based on real material science.

QuantumATK is a tool that can be used when no other data is available. This tool is known as an “ab initio” or “first-principles” approach because it doesn’t require calibration and is based on the solution of fundamental quantum equations. This tool is used to simulate the behavior of materials at the atomistic scale and provide insight into the precise physical mechanisms that govern material science properties, including electrical, mechanical, chemical, and thermal behaviors. One useful application for QuantumATK for WBG materials is the characterization of traps levels and calculation of diffusion parameters.

More information on characterizing impurities like traps and extracting diffusivity with QuantumATK can be found at https://ieeexplore.ieee.org/document/10319636

GaN and SiC are just two of many promising additions to the world of semiconductor materials. We expect to see a continual stream of new materials and material applications that utilize new types of physics, such as 2D materials and Transition Metal Dichalcogenides (TMDs) as the active channel region in FETs, or in the field of alternative memory device designs that take advantage of novel new physics in the form of spin-driven or ferroelectricity, or even phase-change materials.