Experimental observation of a practical limit on enhancement of the spontaneous emission rate in blue GaN-LEDs by mediating surface plasmons

• Fast-modulation speed of blue-LEDs for Free-Space-Optical communications.
• Experimental study on the practical limit on enhancement of the spontaneous emission rate in SP-mediated blue-LEDs.
• Spontaneous emission rate depending on the separation gap between the active and metallic grating layers.
• 2.5 times enhancement of SER at λ = 441 nm, and separation of 20 nm.
• Degradation of the sample quality due to the damages during the etching processes.

High modulation speed of light-emitting diodes (LEDs) is of primary importance for applications in optical communication. To this end, we experimentally investigated enhancement behaviors of the spontaneous emission rate (SER) of electron–hole pairs in blue InGaN/GaN LEDs by mediating surface plasmons (SPs). The coupling strength of the electron–hole recombination into SPs is controlled by etching the p-GaN layer between the active and metal layers to form thicknesses between 40 nm and 10 nm. While a tendency of increasing SER is theoretically expected for a smaller separation, the maximum value SER enhancement has a practical limit of about 2.5 at λ = 441 nm, and separation of 20 nm due to damage on the p-GaN layer caused by the etching process.