Regulation of ultrafast transport of photoinduced terahertz electron-hole plasma waves in semiconductor junctions under dc bias

Regulating carrier transport at semiconductor interfaces using light is essential for optimizing optoelectronic devices. Recent advancements in ultrafast scanning electron microscopy and finite-element methods have provided deeper insights into photoinduced ballistic carrier dynamics in a silicon $p$-$n$ junction. In this work, we develop a finite-element model to further elucidate carrier-transport mechanisms across the junction and explore the use of dc bias to control hot carrier transport and the oscillatory behavior of plasma waves. Our results reveal that, at low laser fluence, applying a reverse bias to the $p$-$n$ junction significantly enhances carrier-transport efficiency. However, at higher laser fluence, the increased carrier density and Coulomb interactions induce terahertz plasma wave oscillations near the junction. The applied bias voltage plays a critical role in modulating these oscillations and their associated terahertz radiation. These findings suggest that dc bias offers an effective means to control photoinduced carrier transport and plasma wave dynamics in $p$-$n$ junctions, paving the way for high-efficiency, tunable terahertz radiation sources.