摘要
There are various mechanisms of light emission in carbon nanotubes (CNTs), which give rise to a wide range of spectral emission characteristics that provide important information regarding the underlying physical processes that lead to photon emission. Here, we report spectra obtained from individual suspended CNT dual-gate field effect transistor (FET) devices under different gate and bias conditions. By applying opposite voltages to the gate electrodes (i.e., Vg1 = –Vg2), we are able to create a pn-junction within the suspended region of the CNT. Under forward bias conditions, the spectra exhibit a peak corresponding to E11 exciton emission via thermal (i.e., blackbody) emission occurring at electrical powers around 8 μW, which corresponds to a power density of approximately 0.5 MW/cm2. On the other hand, the spectra observed under reverse bias correspond to impact ionization and avalanche emission, which occurs at electrical powers of ~ 10 nW and exhibits a featureless flat spectrum extending from 1,600 nm to shorter wavelengths up to 600 nm. Here, the hot electrons generated by the high electric fields (~ 0.5 MV/cm) are able to produce high energy photons far above the E11 (ground state) energy. It is somewhat surprising that these devices do not exhibit light emission by the annihilation of electrons and holes under forward bias, as in a light emitting diode (LED). Possible reasons for this are discussed, including Auger recombination.
基金
The authors would like to acknowledge support from the Northrop Grumman-Institute of Optical Nanomaterials and Nanophotonics(NG-ION2)(B.W.).This research was supported by the NSF Award No.CBET-1905357(S.Y.)and Department of Energy DOE Award No.DE-FG02-07ER46376(Y.W.).R.K.acknowledges funding from AFOSR Grant No.FA9550-16-1-0306 and National Science Foundation Award No.1610604.R.A.acknowledges a USC Provost Graduate Fellowship.A portion of this work was carried out in the University of California Santa Barbara(UCSB)nanofabrication facility:This work was also carried out in part at the Center for Integrated Nanotechnologies,a U.S.Department of Energy,Office of Science user facility.Y.L.,S.K.D,and H.H.acknowledge partial support of the LANL LDRD program and Y.L.and H..H.acknowledge support from DOE BES FWP#LANLBES22.
