STUDY OF CURRENT-VOLTAGE CHARACTERISTICS OF GALLIUM NITRIDE-BASED LEDs

Abstract

The study of the current-voltage characteristics (I-V characteristics) of LED light sources is key in the design of power supplies with optimal efficiency and long service life. Blue LEDs based on InGaN-GaN, which are used in many lighting structures due to their high brightness, low power consumption and short transient times, were studied. The measurements were performed in dynamic and discrete modes of changing the supply voltage and at low ≤1 mA and high 20 mA injection current levels. The main attention is paid to the results of dynamic measurements, which made it possible to minimize changes in the heterojunction temperature due to self-heating during measurements. An analytical approximation of the experimental characteristics was made using the Gaussian function, with a coefficient of determination R²=0,998. Having a mathematical representation of the I-V characteristic, the differential resistance of the diode was calculated, and its dependence on voltage was presented. Theoretical calculations are confirmed by experimental measurements at different points of the I-V characteristic both at low and at high injection levels. Based on the calculations and experimental measurements in the equivalent electrical circuit of the FYL-3014-50 mW LED, the values of the series and parallel resistances were determined. The value of the parallel resistance was taken as the differential resistance R_p=10⁵ Ohms, determined at a voltage of V=2,5 V and a current injection of I=10^-5 A. The value of the series resistance was taken as the differential resistance R_s=27 Ohms, at a voltage of V=3,2 V and a current injection of 20 mA. These results can be used in the development of pulsed power supply drivers for LEDs with pulse width modulation, both narrow-spectrum and white glow with a luminescent coating based on InGaN-GaN structures.