Brandon Li Launches SemiSim to Visualize Semiconductor Physics

Brandon Li has released SemiSim, an interactive educational simulator designed to let users draw circuits and visualize electromagnetic fields in real-time. The tool aims to demystify the complex physics of semiconductor devices by providing a visual, intuitive interface for modeling electron and hole behavior.

At its core, SemiSim solves two-dimensional Maxwell equations on a grid. In this model, the electric field remains tangent to the screen while the magnetic field is perpendicular to it. This mathematical approach allows the software to simulate how charge carriers move across different materials, with native support for metals, semiconductors, and dielectrics. To bring the tool to a wider audience, Li developed a JavaScript port of the simulator with assistance from Paul Falstad.

The Path to Accessibility

SemiSim began as a personal project for Li, who created the software as a way to deepen his own understanding of semiconductor physics. The goal was to move away from static textbook diagrams and toward a "painting-like" interface where users can actively design circuits and see the immediate physical consequences of their layout. By turning abstract equations into a dynamic visual experience, the tool seeks to make the steep learning curve of electronics education more manageable for students.

Impact on Electronics Education

The ability to visualize charge carrier dynamics—specifically the movement of electrons and holes—is critical for understanding the fundamental building blocks of modern technology. By providing a sandbox for these phenomena, SemiSim lowers the barrier to grasping the inner workings of PN junctions and MOSFETs. This shift from theoretical calculation to visual experimentation allows users to develop a more concrete intuition for how electromagnetic fields dictate the behavior of hardware.

Availability and Distribution

SemiSim is currently distributed across three different platforms to balance accessibility and feature sets. A browser-based version allows for immediate use without installation, while a free desktop version is available via GitHub. For users seeking advanced utility, a paid version is available on Steam, which introduces exclusive features including cloud saves and a community workshop for sharing designs.