SKM 2023 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 44: Nitrides: Devices

HL 44.6: Talk

Thursday, March 30, 2023, 16:30–16:45, POT 112

Intensity fluctuations of infrared and green photodiodes at constant current and its correlation with voltage fluctuations — •Danylo Bohomolov and Ulrich T. Schwarz — Chemnitz University of Technology, Chemnitz, Germany

One important issue for display and sensing applications in LEDs is the fluctuation of light intensity over time. The physical reasons behind this are not fully understood yet, e.g. defect-related blinking is dicussed. In addition, it is known that the noise of these devices has a strong correlation with their lifetime. Consequently, the noise of the infrared and green micro-LEDs will be measured here, after which the similarity of their behaviour will be investigated. Standard derivation and corner frequency between flicker noise and thermal noise are chosen as the main comparison parameters. For this purpose, their spectral power density of intensity fluctuations of the emitted light at constant current is investigated. We use a linear controlled precision current source. A large area Si photodiode with amplification capability is used as detector, and the signal is measured using a low-noise transimpedance amplifier and a 24-bit analog-to-digital converter. In parallel, the voltage of the LED is measured to correlate fluctuations in voltage and intensity. We observe oscillations in the frequency range from 1 Hz to 15 kHz. The first measurements of the infrared LEDs showed the presence of 1/f and Johnson-Nyquist noise in this frequency range as expected.