Abstract
We demonstrate high-performance InGaN/GaN blue light emitting diodes (LEDs) embedded with an air-void layer produced by a dry-etch of nano-pillars in an n-GaN layer grown on patterned sapphire substrate (PSS), filling the space between nano-pillars with SiO2 nano-particles (NPs) and subsequent epitaxial overgrowth. The structure exhibits enhanced output power compared to similarly grown reference conventional LED without the air-void layer. This change in growth procedure contributes to the increase of internal quantum efficiency (IQE) and light extraction efficiency (LEE) resulting in a 13.5% increase of light output. LEE is 2 times more affected than IQE in the modified structure. Simulation demonstrates that the main effect causing the LEE changes is due to the emitted light being confined within the upper space above the air-void layer and thus enhancing the light scattering by the SiO2 NPs and preferential light via front surface.
Highlights
Light emitting diodes (LEDs) and laser diodes are widely used optoelectronic devices, but many important problems still require solving
As an option to decrease the threading dislocation (TD) density and increase the internal quantum efficiency (IQE), epitaxial lateral overgrowth (ELO) has been studied [4]. Another inherent problem of GaN-based LEDs is the low light extraction efficiency (LEE) due to the relatively low angle of total internal reflection (TIR) caused by the large difference between the refractive indices of air and GaN. This limits the extraction of light generated from the multi quantum well (MQW) of LEDs so that only a small portion of the light escapes towards the outside [5]
We demonstrated the advanced LED structure on conventional sapphire substrate (CSS) with GaN nano-pillars filled with SiO2 nano-particles (NPs) to suppress dislocations propagating along the vertical growth direction from the bottom of air-void on CSS, resulting in ~300% increase in optical output power [3]
Summary
Light emitting diodes (LEDs) and laser diodes are widely used optoelectronic devices, but many important problems still require solving. As an option to decrease the TD density and increase the internal quantum efficiency (IQE), epitaxial lateral overgrowth (ELO) has been studied [4] Another inherent problem of GaN-based LEDs is the low light extraction efficiency (LEE) due to the relatively low angle of total internal reflection (TIR) caused by the large difference between the refractive indices of air and GaN. This limits the extraction of light generated from the multi quantum well (MQW) of LEDs so that only a small portion of the light escapes towards the outside [5]. To enhance LEE, air void structures embedded in GaN-based LEDs have been studied, which is useful to increase IQE and the external quantum efficiency (EQE) as a result [6,7,8]
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