Origins of double emission peaks in electroluminescence spectrum from InGaN/GaN MQW LED

InGaN/GaN multiple quantum well (MQW) light emitting diode (LED) wafers with two emission peaks were grown by MOCVD. Transmission electron microscopy (TEM), electroluminescence (EL), and cathodoluminescence (CL) measurements were performed to study the recombination mechanism of the InGaN QWs. It was found that there are different widths of quantum wells in TEM images. Green and blue emissions were separately observed in the EL spectra, which are located at 2.45 and 2.81eV, respectively. The wavelengths for both the blue and green emission do not shift until the injection level reaches 2 × 104 mA/cm2. In monochromatic CL images, the green emission comes from randomly distributed dots and floccules that occupy almost the whole surface. The blue emission comes from the floccules only. It can be concluded that the blue emission is attributed to the irradiative recombination in the QWs, and the green emission is attributed to that in wider QWs and In-rich QDs.