A heterojunction is a microscopic boundary formed by growing two dissimilar crystalline semiconductors, such as silicon and germanium, directly against each other. This bandgap mismatch creates energy barriers that confine electrons or holes to very thin layers, drastically increasing carrier mobility. Engineers use them to build high-frequency transistors, lasers, and highly efficient solar cells.
Heard on the job
The new RF amplifier relies on a silicon-germanium heterojunction to hit that 100 gigahertz switching speed.