The clock frequency is single-digit gigahertz. But digital signals have to propagate through multiple layers of logic gates, so the transistors have to switch much faster.
At a glance, the article doesn't make it clear whether the "terahertz" speed refers to switching frequency or gain bandwidth (fT). You can definitely get transistors with fT in the hundreds of gigahertz range right now.
At a glance, the article doesn't make it clear whether the "terahertz" speed refers to switching frequency or gain bandwidth (fT). You can definitely get transistors with fT in the hundreds of gigahertz range right now.