The InGaN based multiple quantum well (MQW) structure in a commercially available white light emitting diode (LED) was studied by transmission electron microscopy (TEM) and three-dimensional atom probe tomography (APT). The average In mole fraction by three-dimensional (3D) APT was found to be about 18% in the InGaN well which is consistent with the secondary ion mass spectrometry (SIMS) analysis.

The In distribution in the InGaN well layer was analyzed by the iso curve mapping of 3D APT and found to be nonuniform in the InGaN active layer. In clustering or In rich regions in the range of 2–3 nm size were found, in contrast to recent reports. Our results thus indicate that In clustering is essential for high-brightness InGaN based LEDs. We have also observed a discontinuity in the range of 50–100.

Group III-nitride semiconductors have been recognized as very important materials for opto-electronic devices such as light emitting diodes (LEDs) and laser diodes (LDs) for applications in the visible and ultra-violet (UV) regions. To produce highly efficient light emission in LEDs, it is important to realize pure and almost perfect semiconductor materials in epitaxial growth. In most LED materials, it is desirable to have dislocation densities.....

Link to the full article: Phys. Status Solidi RRL 3, No. 4, 100– 102 (2009) / DOI 10.1002/pssr.200903007
Link to the Instrumentation: 3D APT