Effect of in situ degradation on the atomic structure and optical properties of GaN-based green light-emitting diodes

Q Liu,H Shan,B Han,D Han,Y Hou,S Ma,Y Wei,L Shang,B Xu,B Cao,S Zhang,X Hao,Y Yang

doi:10.1063/5.0021659

Abstract

The structure at the atomic scale and optical properties of GaN-based green light-emitting diodes (LEDs) before and after in situ degradation were investigated by spherical aberration corrected scanning transmission electron microscopy and temperature-dependent micro-photoluminescence. Indium (In) interstitial atoms existed in the degraded sample, due to the small-bond-energy In atoms deviating from their normal lattice position, caused by the relaxation of the InGaN well. Both the peak wavelengths of the original and degraded green LEDs had similar temperature-dependent behaviors, due to the localization states in the InGaN well. These wavelengths indicate that the degradation had little influence on the localization states. However, the emission peak of the degraded green LED redshifted by 1.6 nm at 300 K, and the integrated intensity decreased by 36.8%, compared to the peak and intensity of the original sample, respectively. Based on first-principles calculations, the calculated bandgap for the relaxation of the InGaN well was small. Therefore, the wavelength redshifted, and the luminous efficiency of the green LED decreased after degradation. These features are attributed to a decreased bandgap due to the relaxation of the InGaN well; increased defect density, resulting from In interstitial atoms; and an increase in the InGaN well thickness.

Highlights

Theoretical analysis of the degradation mechanism of point defects can explain the generation process; one of such analyses has indicated a diffusion-enhanced square-root increase in the nonradiative recombination centers.9 Armstrong et al reported that an
The structure at the atomic scale and optical properties of GaN-based green light-emitting diodes (LEDs) before and after in situ degradation were investigated by spherical aberration corrected scanning transmission electron microscopy and temperature-dependent micro-photoluminescence
The emission peak of the degraded green LED redshifted by 1.6 nm at 300 K, and the integrated intensity decreased by 36.8%, compared to the peak and intensity of the original sample, respectively

Summary

Introduction

Theoretical analysis of the degradation mechanism of point defects can explain the generation process; one of such analyses has indicated a diffusion-enhanced square-root increase in the nonradiative recombination centers.9 Armstrong et al reported that an. Indium (In) interstitial atoms existed in the degraded sample, due to the small-bond-energy In atoms deviating from their normal lattice position, caused by the relaxation of the InGaN well.

Results

Conclusion