Theoretical demonstration of DBR-assisted super-periodic photonic-crystal light-emitting diodes with narrow divergence angles

Highly-directive light-emitting diodes showing high extraction efficiency are designed and demonstrated based on a two-dimensional super-periodic photonic-crystal structure. With this specific design, a super-periodic photonic-crystal structure can generate a highly directional beam by satisfying the multiple-resonance conditions of distributed Bragg reflectors and the topmost slab. Dependence of the power efficiency on the thickness of the topmost slab and the etching depth of the photonic-crystal holes is then analyzed by the three-dimensional finite-difference time-domain method. From subsequent analyses, it has been determined that >80% of the extracted power could be funneled into a small divergence angle of 30°.