This work investigates the influence of residual stress on the performance of InGaN-based red light-emitting diodes (LEDs) by changing the thickness of the underlying n-GaN layers. The residual in-plane stress in the LED structure depends on the thickness of the underlying layer. Decreased residual in-plane stress resulting from the increased thickness of the underlying n-GaN layers improves the crystalline quality of the InGaN active region by allowing for a higher growth temperature. The electroluminescence intensity of the InGaN-based red LEDs is increased by a factor of 1.3 when the thickness of the underlying n-GaN layer is increased from 2 to 8 μm. Using 8-μm-thick underlying n-GaN layers, 633-nm-wavelength red LEDs are realized with a light-output power of 0.64 mW and an external quantum efficiency of 1.6% at 20 mA. The improved external quantum efficiency of the LEDs can be attributed to the lower residual in-plane stress in the underlying GaN layers.

Here we report InGaN-based red light-emitting diodes (LEDs) grown on ( 2 ¯ 01 ) β-Ga₂O₃ substrates. AlN/AlGaN strain-compensating layers and hybrid multiple-quantum-well structures were employed to improve the crystalline-quality of the InGaN active region. A bare LED showed that peak wavelength, light output power, and external quantum efficiency were 665 nm, 0.07 mW, and 0.19% at 20 mA, respectively. As its forward voltage was 2.45 V at 20 mA, the wall-plug efficiency was 0.14%. The characteristic temperature of the LEDs was 222 K at 100 mA evaluated from the temperature dependence of electroluminescence.

We demonstrated 10 × 10 arrays of InGaN 17 μm × 17 μm micro-light-emitting diodes (μLEDs) with a peak wavelength from 662 to 630 nm at 10 – 50 A / cm 2 . The on-wafer external quantum efficiency reached 0.18% at 50 A / cm 2 . The output power density of the red μLEDs was obtained as 1.76 mW / mm 2 , which was estimated to be higher than that of 20 μm × 20 μm AlInGaP red μLEDs ( ∼ 630 nm ). Finally, we demonstrate that InGaN red/green/blue μLEDs could exhibit a wide color gamut covering 81.3% and 79.1% of the Rec. 2020 color space in CIE 1931 and 1976 diagrams, respectively.

We demonstrated amber InGaN $47\times 47\,\,\mu \text{m}^{{2}}$ micro-light-emitting diodes ( $\mu $ LEDs) with the peak wavelength of 606 nm and full-width at maximum (FWHM) of 50 nm at 20 A/cm ² . The amber $\mu $ LEDs exhibited a 33-nm blue-shift of the peak wavelength and obtain broader FWHMs to approximately 56 nm at 5 to 100 A/cm ² . The peak on-wafer external quantum efficiency was 0.56% at 20 A/cm ² . The characteristic temperature was 50–80 K at 20 to 60 A/cm ² but increased to 120–140 K at 80 to 100 A/cm ² . The strong increase in the characteristic temperature from 60 to 80 A/cm ² could mainly be attributed to the saturation of the Shockley-Read-Hall non-radiative recombination at high current densities.

Here, we report highly efficient InGaN-based red light-emitting diodes (LEDs) grown on conventional c-plane-patterned sapphire substrates. An InGaN single quantum well active layer provides the red spectral emission. The 621-nm-wavelength LEDs exhibited high-purity emission with a narrow full-width at half-maximum of 51 nm. The packaged LED’s external quantum efficiency, light-output power, and forward voltage with a 621 nm peak emission wavelength at 20 mA (10.1 A/cm²) injection current were 4.3%, 1.7 mW, and 2.96 V, respectively. This design development represents a valuable contribution to the next generation of micro-LED displays.

Fabrication of indium tin oxide (ITO) was optimized for InGaN-based amber/red light-emitting diodes (LEDs). A radiofrequency sputtering reduced the sheet resistivity of ITO at low pressures, and a subsequent two-step annealing resulted in a low sheet resistivity (below 2×10⁻⁴ Ωcm) and high transmittance (over 98%) in the amber and red regions between 590 nm to 780 nm. Double ITO layers by sputtering could form an excellent ohmic contact with p-GaN. Application of the double ITO layers on amber and red LEDs enhanced light output power by 15.6% and 13.0%, respectively, compared to those using ITO by e-beam evaporation.