High extraction efficiency GaN-based light-emitting diodes on embedded SiO2 nanorod array and nanoscale patterned sapphire substrate

Abstract

In this paper, GaN-based LEDs with a nanoscale patterned sapphire substrate (NPSS) and a SiO2 photonic quasicrystal (PQC) structure on an n-GaN layer using nanoimprint lithography are fabricated and investigated. The light output power of LED with a NPSS and a SiO2 PQC structure on an n-GaN layer was 48% greater than that of conventional LED. Strong enhancement in output power is attributed to better epitaxial quality and higher reflectance resulted from NPSS and PQC structures. Transmission electron microscopy images reveal that threading dislocations are blocked or bended in the vicinities of NPSS layer. These results provide promising potential to increase output power for commercial light emitting devices.

Investigation and Comparison of the GaN-Based Light-Emitting Diodes Grown on High Aspect Ratio Nano-Cone and General Micro-Cone Patterned Sapphire Substrate

“…As compared to the previous work [29], the aspect ratios of the structure with NPSS and embedded SiO nanorod array and the structure with HAR-NPSS in this paper are indeed much different. The aspect ratio of the former structure is approximately 0.4, while it of the current structure is approximately 1.12.…”

“…However, we should note that the 48% of light output power enhancement is contributed from both effects of the NPSS and embedded SiO nanorod array. For the LED only with the NPSS structure, the light output power enhancement is only 35% [29]. In addition, the chip sizes between these two researches are different.…”

“…In this study, the high aspect ratio cone-type nano-patterned sapphire substrate (HAR-NPSS) was used to decrease the defect density and improve the quality of GaN LEDs. A nano-imprint lithography (NIL), which is a high throughput, rapid and repeating process for mass production, was utilized to fabricate a HAR-NPSS with a 12-fold a photonic quasi-crystal (PQC) pattern [24]- [27]. In order to fabricate a high depth HAR-NPSS, the NIL was processed with a deep imprint-mold with a high depth of 700 nm.…”

Modeling the effect of acceptor-type traps on internal electric field of a GaN-pin device phenomenon

“…In order to reduce the low leakage current density of the high-power devices using both SiC and free-standing GaN are instead of sapphire substrate [1,2], but these substrates are non-cheap. Recently, the issue has resulted in a repaid expansion of efforts to develop alternatives utilizing patterned-sapphire substrates (PSS) and nano patterned-sapphire substrates (NPSS), that can elevate the device optical/electrical characteristics [3]. In addition to the Si power devices, a larger breakdown voltage focuses on the drift layer thickness of the high power devices.…”

Improving the Light-Emitting Efficiency of GaN LEDs Using Nanoimprint Lithography

“…al. [59] used a similar thermal pressing technique combined with ICP etching to create a convex NPSS with a periodicity of 750 nm and a diameter of 450 nm. The height of the NPSS structures was 182 nm.…”