III-nitride-based microarray light-emitting diodes with enhanced light extraction efficiency

In this paper, the enhancement of light extraction efficiency in III-nitride-based light-emitting diodes (LEDs) with an array of microstructures is demonstrated numerically and experimentally at the near-ultraviolet (n-UV) spectral region. Two different microstructures are adopted to study the mechanism, including the shallow etching of microstructures on the indium-tin-oxide (ITO) p-contact and the deep etching of microholes through the InGaN/GaN multiple-quantum-well (MQW) active structure and down to the n-type GaN layer. Multiple point sources with TE and TM polarizations in the MQW region are utilized in the finite-difference time domain (FDTD) analysis to model the behaviour of LED. The simulated beam patterns of both LEDs reveal that the microstructures act as diffraction gratings to extract guided light in the n-type GaN layer. The measured results of beam patterns also verify the prediction in the numerical analysis.