Photoluminescence of single-walled carbon nanotubes in field-effect transistors

Abstract

We have studied the photoluminescence (PL) of individual single-walled carbon nanotubes(SWNTs) placed in field-effect transistor structures. The SWNTs were suspended in the airso that strong PL was obtained. When an external bias voltage was applied to the device,no spectral changes could be detected, but the intensity drastically increased ordecreased. This behaviour is explained by the injection/extraction of carriersfrom/to the electrodes by the electric field. In the case of p-type FETs in the air,PL intensity increased due to hole injection by applying a small negative gatebias. After the device was heated in vacuum, the maximum PL intensity wasobtained at zero gate bias. This can be explained by the change in the interfacebetween the SWNT and contact electrodes. The drain field dependence of thePL intensity shows a monotonic decrease, which is explained by a competitionbetween the recombination lifetime and transit time of photo-excited carriers inthe SWNT. Using analytical steady-state rate equations on carrier density inthe SWNT, the relation between the recombination lifetime and carrier transittime has been evaluated. The carrier saturation velocity has also been estimated.