Ultrafast photocurrent measurement of the escape time of electrons and holes from carbon nanotube PN junction photodiodes

TL;DR

This study uses ultrafast photocurrent measurements to analyze electron and hole escape times in carbon nanotube PN junction photodiodes, revealing bias-dependent decay times and energy-related effects.

Contribution

It introduces a model that explains photocurrent suppression dynamics based on carrier escape times and effective mass in carbon nanotube photodiodes.

Findings

Photocurrent suppression occurs at zero delay between pulses.

Decay time scales inversely with applied bias voltage.

Escape times are longer for higher photon energies above E22.

Abstract

Ultrafast photocurrent measurements are performed on individual carbon nanotube PN junction photodiodes. The photocurrent response to sub-picosecond pulses separated by a variable time delay {\Delta}t shows strong photocurrent suppression when two pulses overlap ({\Delta}t = 0). The picosecond-scale decay time of photocurrent suppression scales inversely with the applied bias VSD, and is twice as long for photon energy above the second subband E22 as compared to lower energy. The observed photocurrent behavior is well described by an escape time model that accounts for carrier effective mass.