Analysis of the mechanisms by which sputtered AlN nucleation layers enhance the performance of red InGaN-based LEDs

Abstract

This work proposed to modulate the strain of underlying GaN layers using different thicknesses of sputtered AlN nucleation layer to achieve long-wavelength red InGaN mini-light-emitting diodes (mini-LEDs). The increase in thickness of sputtered AlN from 15 nm to 60 nm could reduce the compressive strain in epitaxial GaN layers, which led to a shift in the peak wavelength of InGaN LEDs ranging from 633 nm to 656 nm at 1 A/cm2. However, a significant decrease in external quantum efficiency (EQE) was observed when the sputtered AlN thickness was increased from 45 nm to 60 nm. We found that the EQE and peak wavelength (PW) of the red mini-LEDs with 45-nm sputtered AlN at 1 A/cm2 were 8.5% and 649 nm, respectively. The study revealed that varying the thickness of AlN nucleation layers could extend the emission of red InGaN mini-LEDs toward longer wavelengths with a slight EQE loss.