Electrical Engineering Department
BS in Electrical Engineering
This study analyzes optical confinement factor and light emitting mode order for three different GaN LEDs: a conventional LED, thin Film LED, and thin Film LED with a photonic crystal (PhC) grating. For the first structure, we increase the thickness of AlxGa1-xN from 0 to 600nm, alter the x composition in AlxGa1-xN from 0.05 to 0.2 in steps of 0.05, and adjust the p-GaN and n-GaN thicknesses each from 0 to 200nm. For the second structure, we alter the n-GaN substrate thickness from 300-1000nm in steps of 100nm and 1000-4000nm in steps of 1000nm. These simulations show that increasing the substrate thickness causes the light emitting mode order to increase. The higher the mode, the more current is needed to make the device emit light. Higher current leads to shorter device lifetime. The last structure contains a photonic crystal grating with a period T = 100nm, 230nm, 460nm, 690nm, 920nm, 1500nm, 2000nm, 3000nm and 50% duty cycle. For each grating period, we display the effects on optical confinement factor and optical field intensity. The results show that changing the grating period does not affect the mode order, but does affect the optical field intensity. A larger grating period corresponds to lower optical field intensity. Maximizing optical field intensity increases the brightness of the device. The simulation method above can be used to improve the efficiency, brightness, and lifetime of GaN LEDs by reducing the effects of transverse mode coupling and maximizing the optical field intensity.