| Abstract [eng] |
This study investigates the low-frequency electrical and optical noise characteristics of InGaN-based blue light-emitting diodes (LEDs) with peak wavelengths of 455 nm and 470 nm before and after accelerated aging. The aim of this investigation was to clear up noise origins and their relation to the device aging processes. It focuses on understanding how aging affects carrier transport, defect generation, optical emission, and reliability of optoelectronic devices through noise diagnostics. A literature review was conducted on different noise mechanisms in semiconductor devices, including thermal noise, shot noise, generation–recombination noise, random telegraph signal noise, and 1/f noise. Particular attention was given to the role of low-frequency noise as a sensitive, non-destructive diagnostic tool for detecting structural defects, degradation processes, leakage currents, and reliability issues in LEDs and other optoelectronic devices. Experimental investigations were carried out using 455 nm and 470 nm blue LEDs under controlled laboratory conditions. Electrical current–voltage characteristics, optical output power, electrical voltage noise spectral density, optical noise spectral density, and cross-correlation between electrical and optical fluctuations were measured before and after 30 h of accelerated aging. Noise spectra were analyzed in the frequency range from 10 Hz to 20 kHz at different operating currents. The results demonstrated typical 1/f noise behavior in both LEDs, with the spectral density decreasing with increasing frequency. The 455 nm LED exhibited higher optical output power and significantly larger electrical and optical noise levels compared to the 470 nm LED. After aging, the optical output power of the 455 nm LED decreased, while optical and electrical noise intensity increased. The 470 nm LED showed only minor changes in electrical and optical characteristics. Correlation analysis between electrical and optical fluctuations revealed a strong positive correlation for the 455 nm LED before aging, indicating efficient radiative recombination within the active region. After aging, the correlation became negative for both LEDs, suggesting the formation of current leakage paths and degradation-related defects that affect carrier transport. |
