We study nano-scale ITO top transmission gratings to improve light extraction efficiency (LEE).
We use the finite difference time domain (FDTD) method to measure light extraction from a
device with various grating structures and layer thicknesses. We simulate our device using a twodimensional
model with top triangular-gratings in a crystal lattice arrangement described by
grating cell period (Α), grating cell height (d), and grating cell width (w). We also define ITO
layer thickness (L) as the layer between the p-type GaN and the ITO surface layers. Simulation
models vary in grating period, grating width, and ITO layer thickness. Our simulations monitor
the amount of light emitted from the top, bottom, and sides of the LED model. We calculate the
total light extraction and determine which grating duty cycle maximizes LEE. We found that
adding a nano-scale grating with optimum duty cycle can achieve 165.67% and 136.77% LEE
improvement, respectively, for ITO layer thickness of 230nm and 78nm.