Electroluminescence of individual single-walled carbon nanotubes down to ∼15K is measured. We observe electrically driven light emission from suspended quasimetallic nanotubes in vacuum down to ∼15K and under different gas pressures at room temperature. Light emission is found to originate from hot electrons in the presence of electrically driven nonequilibrium optical phonons. Reduced light emission is observed in exponential manner as electron and optical phonon temperatures in the nanotube are lowered by lower ambient temperature or higher gas pressure. The results reveal over wide ambient conditions, light emission in a suspended tube is from thermally excited electron-hole recombination.
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