GaN-based light emitting diodes with embedded SiO2 pillars and air gap array structures

Abstract

We demonstrated GaN-based light emitting diodes (LEDs) with different embedded heights of SiO2 pillars and air gap array structures. The air gap on top of the SiO2 pillars were also realized using the enhanced epitaxial lateral overgrowth mode. With the embedded SiO2 pillars and air gap array structures, we achieved a smaller reverse leakage current due to the lateral growth-induced crystal quality improvement. Moreover, under 20 mA current injections, the output powers were 3.04, 4.23, 4.66, and 4.44 mW for conventional LED, LEDs with embedded 200 and 500 nm height of SiO2 pillars and air gaps, 500 nm height of SiO2 pillars and air gaps, and 700 and 400 nm height of SiO2 pillars and air gaps, respectively. We found that the embedded 500 nm height SiO2 pillars and 500 nm height air gap array structures could enhance LED output power by more than 50% due to the enhanced guided-light scattering efficiency in our study.

Improving the optical performance of InGaN light-emitting diodes by altering light reflection and refraction with triangular air prism arrays

“…It is also noted that the light output power measured at the back side is slightly higher than that measured at the front side for all the LEDs [12]. The observed enhancement in light output power with TAP arrays is higher than the values recently reported for LEDs made with different air-void structures [8][9][10]. This observation signifies the importance of the geometrical shape of air-voids.…”

“…Formation of air-voids at the vicinity of sapphire/GaN interface is also an efficient method for improving LEE of LEDs [7][8][9][10][11]. To date, air-voids of various forms have been studied by different groups.…”

Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2AlN/Sapphire Template

“…Recent studies have proposed several useful growth techniques to improve the crystal quality, such as epitaxial lateral overgrowth (ELOG) [4][5][6], pendeo-epitaxy (PE) [7], maskless PE [8], cantilever epitaxy [9], facet-controlled epitaxial lateral overgrowth (FACELO) [10,11], SiN x /GaN buffer layer [12], abbreviated growth mode [13][14][15], and freestanding GaN substrates [16][17][18]. Patterned sapphire substrate [19] and embedded air voids method [20,21] have been developed to further enhance the light extraction efficiency (LEE) of light-emitting diodes (LEDs). However, embedded air voids method has been widely used.…”

Surface plasmon-enhanced light-emitting diodes with silver nanoparticles and SiO2 nano-disks embedded in p-GaN

“…The PL enhancement can be attributed mostly to the SiO 2 nano-disks embedded in the p-GaN layer, which scatter the propagating light randomly and improve the light extraction efficiency of the LEDs. [12][13][14][15] To confirm that the improvement of internal quantum efficiency (g int ) is caused by the increase in the spontaneous recombination rate through the quantum well (QW)-LSPs coupling, the temperature-dependent PL was measured at temperatures ranging from 10 to 300 K. Figure 3(b) shows an Arrhenius plot of the normalized PL intensity for the SP-enhanced LEDs with and without SiO 2 nano-disks in the p-GaN layer. The value of g int for the LEDs can be estimated by comparing the integrated PL intensities, assuming that the g int is 100% at 10 K. 16 The value of g int for the SP-enhanced LEDs with both Ag nanoparticles and SiO 2 nano-disks was estimated to be 38%, which is about three times higher than that (12%) of the LED without Ag nanoparticles.…”

“…7,17 However, the electrical properties of the LEDs with SiO 2 nano-disks, which act as LEO masks, are nearly the same as those of LEDs without Ag nanoparticles, because the SiO 2 nano-disks significantly reduce the defects induced by the Ag nanoparticles and improve the electrical properties of the LEDs. [14][15][16] The reverse-bias leakage current of SP-enhanced LEDs with both Ag nanoparticles and SiO 2 nano-disks, as shown in Fig. 4(a), is believed to be due to the defects induced by the Ag nanoparticles in the window regions between the SiO 2 nano-disks.…”