Terahertz Pulse Generates 1,000-Fold Increase in Electron Density

http://int.saci.kyoto-u.ac.jp/?p=2336
The study of carrier multiplication has become an essential part of many-body physics and materials science. Assistant Prof Hideki Hirori and co-workers observed that when exposed to a single-cycle electric field pulse at the 1000 GHz (terahertz) frequency range, a sample of standard semiconductor material (gallium arsenide, GaAs) burst an avalanche of electron-hole pairs (excitons) 1,000-times more abundant than initial states only on the picosecond (10-12 s) time scale. The observed bright luminescence associated with carrier multiplication suggests that carriers coherently driven by a strong electric field can efficiently gain enough kinetic energy to induce a series of impact ionizations. These just-released results with the world strongest terahertz pulses demonstrate the rich potential that lies in the study of terahertz radiation.

This carrier multiplication directly affects nonlinear transport phenomena in ultra-high-speed transistors and plays a key role in designing efficient solar cells and electroluminescent emitters and highly sensitive photon detectors.

Related Information 1. H. Hirori, K. Shinokita, M. Shirai, S. Tani, Y. Kadoya, and K. Tanaka: Nature Commun. 2, 594 (2011).
2. H. Hirori, A. Doi, F. Blanchard, and K. Tanaka: Appl. Phys. Lett. 98, 091106 (2011).