In-situ mapping of electroluminescent enhancement of light-emitting diodes grown on patterned sapphire substrates

The mechanism for enhancing extraction efficiency of light emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) was observed by the in-situ lateral electroluminescence (EL) mapping using optical microscopy equipped with a laser energy profiler. The observed spatial intensity distribution of epilayers, varying from epilayer to epilayer on the lateral surface of the PSS LED chip, revealed that the perimeter scattering on the convex facets of PSSs converges the propagation of emitted light with random directionality into a spot near the top surface of the buffer layer. Moreover, this in-situ sidewall mapping implied that the enhancement of light extraction of the PSS LED is due to reducing the total internal reflection effect, resulting from the spot located closer to the LED/air interface. Simulated results and EL images of convex patterns on the PSS surface were consistent with sidewall surface-based observations. Published by AIP Publishing.