Gallium nitride-based light-emitting diodes with embedded air voids grown on Ar-implanted AlN/sapphire substrate

Abstract

GaN-based light-emitting diodes (LEDs) grown on sapphire with ex situ AlN nucleation layer prepared by radio-frequency sputtering were investigated. GaN-based epitaxial layers grown on the Ar-implanted AlN/sapphire (AIAS) substrates exhibited selective growth and subsequent lateral growth due to the difference of lattice constants between the implanted and implantation-free regions. Consequently, air voids over the implanted regions were formed around the GaN/AlN/sapphire interfaces. We proposed the growth mechanisms of the GaN layer on the AIAS substrates and characterized the LEDs with embedded air voids. With a 20 mA current injection, experimental results indicate that the light output power of LEDs grown on the AIAS substrates was enhanced by 25% compared with those of conventional LEDs. This enhancement can be attributed to the light scattering at the GaN/air void interfaces to increase the light extraction efficiency of the LEDs.

Growth and characterization of GaN-based LED wafers on La0.3Sr1.7AlTaO6 substrates

“…For LED chips on LSAT substrates, even when the injection current increases to 100 mA, the light output power still exhibits an upward trend without saturation, indicating excellent electronic properties which are comparable to the conventional GaN-based LEDs grown on sapphire. 52,53 It can be also noted that the light output power for LED on LSAT is some higher than that of LED on sapphire. For example, at an injection current of 20 mA, the light output powers for LEDs on LSAT and sapphire are 4.3 mW and 3.5 mW, respectively, Fig.…”

“…This enhancement in light output for the LED on LSAT might be partly attributed to the uniformity of current spreading in the LED on LSAT substrates due to the better crystalline quality of epitaxial layers, which enhances internal quantum efficiency (IQE) and extraction efficiency. 52,54,55 Fig. 10b illustrates the relationship between the injection current (I) and forward voltage (V) for LED chips on both LSAT and sapphire substrates at room temperature.…”

“…Likewise, we attribute the lower forward voltage of LED on LSAT to its higher crystalline quality than that on sapphire, which reduces the series resistance of the chip. 52,54,55 Evidently, the lattice matched LSAT substrate has a signicant impact on LED device performance. However, further investigations reveal that this GaN-based LED exhibits a relatively strong efficiency-droop effect with the further increment of injection current, which, we believe, should be related to the device structure design of the LED wafer and the growth conditions adopted in this work.…”

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

“…Recently, Lai et al reported an ex situ AlN buffer layer deposited by sputter, which yielded an interruption-free GaN epitaxy [28]. To further improve the light extraction efficiency, Sheu et al implanted Ar into a sputtered AlN nucleation layer, and their results showed that the GaN-based epitaxial layer grown on implanted regions has lower growth rates than the implantation-free regions, which eventually form the embedded air voids [29][30][31].…”

A new system for achieving high-quality nonpolar m-plane GaN-based light-emitting diode wafers

“…We attribute the lower forward voltage of the LED chip grown on LiGaO 2 (100) substrate to the lower series resistance in the LED chip on the LiGaO 2 (100) substrate of $7 U compared with that on the c-plane sapphire substrate of $10 U. 4,[37][38][39][40][41][42] Furthermore, the EQE for LED chips on LiGaO 2 (100) and c-plane sapphire substrates were also studied. Fig.…”