Impurity-related photoluminescence from InGaN led material

This paper explains the quantitative nature of the major emission band in Nichia's LEDs, namely InGaN/AlGaN/GaN high-brightness blue LEDs which represent a major breakthrough in short-wavelength visible light sources. The experimental low-temperature and room-temperature spectra are obtained by photoluminescence. A broad impurity-related PL band, with an undulated envelope centered at approx.465 nm, is observed at both temperatures when the pump beam illuminates the active region. In contrast, when the pump beam illuminates the GaN region under the n-side contact, only a weak yellow emission, centered at approx.560 n is observed. The room temperature blue spectral band is very similar to the electroluminescence spectrum. Concludingly, it is emitted from the active region of the diode, intentionally doped with Zn acceptors and heavily doped with Si donors. The active region may also contain some native donor-type defects usually present in group-III nitrides. In the interpretation of the blue emission band, all of these impurity levels are invoked.