Anomalous Poole-Frenkel mode of current-conduction mechanism in the P-I-N thin-film light-emitting diodes

The current density-applied voltage (J-V) characteristics of the p-i-n thin film light-emitting diode (TFLED) were studied. It is found that when the applied voltage is less than the threshold voltage, the current densities of reverse and forward bias are essentially equal. This indicates that the current is limited by the i-layer, which has the highest resistance. In order to study the current-conduction mechanism in the i-layer, numerical approximation in a one-dimensional model is used to calculate the internal distributions of the potential, electric field, and carrier concentration, etc. The theory of anomalous Poole-Frenkel emission gives a calculated result, which agrees with the experimental result. The relationship between the implicated generation rate and radiative recombination rate with electric field is then analyzed. It is found that the electron impact ionization is the primary cause of electron-hole pairs production which upon recombination results in light emission in the i-layer. The current density was calculated by setting appropriate initial conditions for ionization. Radiative recombination rate needed to fit depends on the magnitude of electric field in the i-layer, being slower as the magnitude of electric field increases.