Probing the indium distribution of InxGa1-xN quantum wells with atomic resolution
EMSL Project ID
47602
Abstract
Lighting consumes one of the largest portions of the nation’s energy, yet the majority of light sources are grossly inefficient. One of the more promising systems for visible light emission, GaN/InxGa1-xN/GaN quantum well thin films, has been plagued by an unresolved debate as to the homogeneity of the InGaN layers. The efficiency of InGaN LEDs is almost an order of magnitude lower than ideally expected, but the fundamental reasons for this rift remain poorly understood. InN-rich inhomogeneities may play an important role in reducing the efficiency, but there is not a clear consensus that any degree of phase separation occurs. Previous studies have largely relied upon high resolution transmission electron microscopy (TEM), which has been shown to induce phase separation under certain conditions, due to electron beam damage. As the films are only 2-5 nm thick and the potential InN-rich clusters the same size or smaller, atom probe tomography (APT) is one of the only other tools with both the spatial and mass resolution needed to observe the presence of any clustering (the mass resolution being far superior to TEM). Here we propose to use a combination of TEM and APT to observe the InGaN films, both before and after observation by TEM. An additional obstacle to a universally acceptable resolution of this debate has been the potential variability between growth conditions and sample processing between groups. For this study, samples have been obtained from prominent groups on both sides of the debate, as well as from industry. This combination of samples and techniques provides a uniquely definitive opportunity to answer these divisive and fundamental questions.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2012-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members