Asymmetric external electric field effects on luminescence intensity of InGaN single-quantum-well light-emitting diode

Temperature dependence of electroluminescence (EL) spectra of the super-bright green InGaN single-quantum-well (SQW) lightemitting diode (LED) has been studied over a wide temperature range (T=15-300 K) and as a function of injection current level. The EL intensity efficiently increases due to reduced non-radiative recombination processes when temperature is slightly decreased to 140 K from 300 K. However, with further decrease of temperature down to 15 K, it drastically decreases due to the reduced carrier capture. In order to pursue origins of the EL quenching at low temperatures, bilateral electric field dependence of the quantum efficiency have been studied at 15 K by photoluminescence (PL) measurements. It is found that the PL intensity gradually decreases with increasing the reverse bias voltage down to –10 V due to tunneling escape of the carrier out of the well. On the other hand, while the PL intensity increases with increasing the forward bias voltage up to 2 V, however, drastic reduction of the PL intensity is observed with further increase of the forward bias voltage up to 4.25 V. This PL quenching in both field directions means that spatial separation of the electron and holes plays an important role in the EL efficiency because of the existence of large internal piezoelectric and spontaneous field. These results suggest that both internal and external field effects are crucial to the unique temperature dependence of the EL efficiency.