Nanoscale Mapping of the Structural Relaxation in Microstructured In_xGa_1−xN Pseudosubstrates by Scanning X‐ray Diffraction Microscopy

Abstract

The technological advancement of mobile devices for virtual and augmented reality requires displays that are faster, more energy‐efficient, and of higher resolution. InxGa1−xN‐based micro‐light‐emitting diodes (LEDs) have the potential to realize such advanced displays thanks to their ability to provide emission of red, green, and blue light simply by tuning the In concentration. However, efficient emission in the red still remains a challenge, as it requires high In contents (≈30–40%) that are unobtainable in InxGa1−xN epitaxial layers pseudomorphically strained to GaN substrates. Research efforts have therefore focused on achieving elastic relaxation of the active InxGa1−xN portion of the LED device to allow greater In incorporation, e.g., through the addition of partially relaxed intermediate InxGa1−xN layers in the heterostructure. Herein, the extent of strain relaxation in InxGa1−xN pseudosubstrates grown on GaN‐on‐sapphire substrates as induced by patterning in mesas 10 μm2 in size is evaluated. Using synchrotron‐based scanning X‐ray diffraction microscopy, the lattice strain and tilt are mapped in a single mesa as well as in an ensemble of mesas with ≈60 nm spatial resolution, demonstrating the effectiveness of the processing route in producing high‐quality, partially relaxed InxGa1−xN pseudosubstrates.