Influence of injection current and temperature on electroluminescence in InGaN/GaN multiple quantum wells

Electroluminescence (EL) spectra of blue InGaN/GaN multiple-quantum-well light-emitting diode (LED) have been investigated over a wide range of injection current (0.001–200 mA) and at various temperatures (6–300 K). Surprisingly, with increasing the injection current the EL peak energy shows an initial blueshift accompanied by a broadening of the EL linewidth at low temperatures (below 30 K). This trend differs from the usual photoluminescence (PL) measurement results, which have shown that with increasing the optical excitation power the PL peak energy gave an initial blueshift accompanied by a narrowing of the PL linewidth at low temperatures. The anomalous current behavior of the EL spectra may be attributed to electron leakage results in the failure of Coulomb screening effect and the relative enhancement of the low-energetic localized state filling at low temperatures and low currents. The electron leakage for the LED is further confirmed by both the current dependence of the EL intensity and the temperature dependence of the EL efficiency.