Can impact excitation explain efficient carrier multiplication in carbon nanotube photodiodes?
We address recent experiments (Science 2009, 325, 1367) reporting on highly efficient multiplication of electron-hole pairs in carbon nanotube photodiodes at photon energies near the carrier multiplication threshold (twice the quasi-particle band gap). This result is surprising in light of recent experimental and theoretical work on multiexciton generation in other confined materials, such as semiconducting nanocrystals. We propose a detailed mechanism based on carrier dynamics and impact excitation resulting in highly efficient multiplication of electron-hole pairs. We discuss the important time and energy scales of the problem and provide analysis of the role of temperature and the length of the diode.
Baer
Roi
R
Fritz Haber Center for Molecular Dynamics, the Chaim Weizmann Institute of Chemistry, the Hebrew University of Jerusalem, Jerusalem 91904, Israel. roi.baer@huji.ac.il
Rabani
Eran
E