Abstract
We employed a patterned current blocking layer (CBL) to enhance light output power of GaN-based light-emitting diodes (LEDs). Nanoimprint lithography (NIL) was used to form patterned CBLs (a diameter of 260 nm, a period of 600, and a height of 180 nm). LEDs (chip size: 300 × 800 µm2) fabricated with no CBL, a conventional SiO2 CBL, and a patterned SiO2 CBL, respectively, exhibited forward-bias voltages of 3.02, 3.1 and 3.1 V at an injection current of 20 mA. The LEDs without and with CBLs gave series resistances of 9.8 and 11.0 Ω, respectively. The LEDs with a patterned SiO2 CBL yielded 39.6 and 11.9% higher light output powers at 20 mA, respectively, than the LEDs with no CBL and conventional SiO2 CBL. On the basis of emission images and angular transmittance results, the patterned CBL-induced output enhancement is attributed to the enhanced light extraction and current spreading.
Highlights
InGaN/GaN-based light-emitting diodes (LEDs) are of significant importance because of their use in various applications such as backlight unit (BLU) for display and solid-state lighting [1,2,3]
The LEDs with a patterned SiO2 current blocking layer (CBL) yielded 39.6 and 11.9% higher light output powers at 20 mA, respectively, than the LEDs with no CBL and conventional SiO2 CBL
On the basis of emission images and angular transmittance results, the patterned CBL-induced output enhancement is attributed to the enhanced light extraction and current spreading
Summary
InGaN/GaN-based light-emitting diodes (LEDs) are of significant importance because of their use in various applications such as backlight unit (BLU) for display and solid-state lighting [1,2,3]. In addition to the enhancement of current injection (by forming low contact resistances) [6,7], different techniques for increasing light extraction efficiency (LEE), e.g., surface roughening [8,9,10], patterned sapphire substrate (PSS) [11,12,13], and photonic crystal (PC) structures [14,15,16], have been actively investigated in order to increase EQE These efforts notwithstanding, both electrical and optical losses that originate from current crowding (due to resistive p-GaN) and photon absorption around the opaque p-type pad still remain to be challenging issues. In order to maximize the LEE, it is important to minimize photon absorption associated with the opaque p-pad and the LED chip, and current crowding
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