Electrical conduction and electroluminescence in nanocrystalline silicon-based light emitting devices

Electrical transport and light emission properties of plasma-enhanced chemical vapor deposition grown light emitting devices LEDs based on nanocrystalline silicon have been studied. Various active layer compositions have been used. Electroluminescence and current-voltage measurements have been performed on metal-oxide-semiconductor structures. We found that Poole–Frenkel emission and trap-assisted tunneling between traps located at the nanocrystalline silicon interfaces are consistent with the measurements. The interface trap density was estimated. Its dependence on the composition of the active layer is discussed. We propose an equivalent electrical circuit model for the LED based on complex impedance measurements. Nanocrystalline silicon electroluminescence in the near infrared region is explained by hot-electron injection and impact ionization mechanism. It is concluded that the trap-assisted tunneling and charge trapping limit the external power efficiency of this kind of devices. © 2008 American Institute of Physics.