Abstract
A p-i-n junction diode based on the selectively doped single-walled carbon nanotube (SWCNT) had been investigated, in which two opposite ends of individual SWCNT channel were doped into the p- and n-type SWCNT respectively while the middle segment of SWCNT was kept as the intrinsic. The symmetric and asymmetric contacts were used to fabricate the p-i-n junction diodes respectively and studied the effect of the contact on the device characteristics. It was shown that a low reverse saturation current of ~20 pA could be achieved by these both diodes. We found that the use of the asymmetric contact can effectively improve the performance of the p-i-n diode, with the rectification ratio enhanced from ~102 for the device with the Au/Au symmetric contact to >103 for the one with the Pd/Al asymmetric contact. The improvement of the device performance by the asymmetric-contact structure was attributed to the decrease of the effective Schottky-barrier height at the contacts under forward bias, increasing the forward current of the diode. The p-i-n diode with asymmetric contact also had a higher rectification ratio than its counterpart before doping the SWCNT channel, which is because that the p-i-n junction in the device decreased the reverse saturated current.
Highlights
A p-i-n junction diode based on the selectively doped single-walled carbon nanotube (SWCNT) had been investigated. In this kind of diode, two opposite ends of individual SWCNT channel were doped by triethyloxonium hexachloroantimonate (OA) and polyethylene imine (PEI) into the p- and n-type SWCNT respectively while the middle segment of SWCNT was kept as the intrinsic to result in the formation of p-i-n junction diode for good photovoltaic effect
The use of the asymmetric contact in the SWCNT p-i-n diode reduced the barrier between the metal electrode and SWCNT, causing the forward current increased by about one order of magnitude and a rectification ratio of > 103
The sharp G-band showed the semiconductor properties of the SWCNTs, and the G-band/D-band intensity ratio was more than two order of magnitudes, indicating that the number of defects in the SWCNTs was very small and graphitization degree of the SWCNTs was high
Summary
The semiconducting SWCNTs (semiconductor purity ~ 99%) was used to fabricate the devices. The reason for the rectification characteristics of the device was due to the p- and n-type doping of the OA and PEI on the two ends of the SWCNT channel respectively (Fig. 2b). To study the effect of the contact, the SWCNT p-i-n junction diode with asymmetric contact was fabricated and investigated by using the metals with different work function (Pd and Al) as the source and drain (Fig. 3a). The device characteristics of the asymmetric-contact SWCNT p-i-n diode was tested, showing a rectification ratio of 1.2 × 103. The symmetric and asymmetric contacts were used to fabricate the diodes respectively Both kinds of diodes showed the typical rectification characteristics. The asymmetrically-contacted SWCNT p-i-n junction diode with a high rectification ratio is promising to be applied as good photovoltaic device or be used in next-generation integrated circuit
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