Light emission from nanocrystalline Si thin-film light emitting diodes due to tunneling carrier injection

Electroluminescence (EL) from nanocrystalline Si ($\mathrm{nc}$ -Si) has been studied by using thin-film light emitting diodes with a structure of ${\mathrm{glass/SnO}}_{\mathrm{2}}\mathrm{/p-}\mathrm{type}$ $\mathrm{nc}$ -Si/Al. When positive bias voltages are applied on the ${\mathrm{SnO}}_{\mathrm{2}}$ electrode, light emission from the $\mathrm{nc}$ -Si occurs with a peak energy of 1.57 eV at room temperature. When the temperatures is increased from 100–350 K, both the EL and photoluminescence (PL) peak energies shift to red. In addition, both the integrated EL and PL intensity rapidly decrease when the temperatures is increased over 200 K. Considering the similar temperature dependence found on the EL and the PL properties, the EL is attributed to the radiative recombination of electrons injected from the Al electrode and holes in the $p$ -type $\mathrm{nc}$ -Si layer. From the analysis of the current–voltage characteristics, electron tunneling at the interface of $\mathrm{nc}$ -Si/Al appears to be the most probable mechanism for the electron injection.