Optoelectronics with Carbon Nanotubes

Figure V-2. (a) Schematic illustration and (b) scanning electron microscope image of
CNT film diodes with split top gates (TG1 and TG2). The white scale bar on lower
left is 5 μm long.
3. Transport characteristics of the CNT film diode
As we saw in the case of the single-tube CNT diode, good transport behavior is critical
for efficient light emission. This is not surprising since the radiative recombination rate of
excitons in CNTs is much smaller than the non-radiative recombination rate. Here, we discuss
electronic transport of CNT film devices with top-split gate to confirm that they do indeed
behave as diodes.
(a)
(b)
The electrical transfer characteristics of two devices with different channel lengths (4 μm
and 6 μm) are shown in Figure V-3 (a) and (b). We see that the fundamental requirement for
CNT diode construction, namely the ambipolar behavior upon gate-sweeping, is satisfied in these
devices. The almost symmetric, ambipolar transfer characteristics of the devices indicate that
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