Determination of Temperature and Thermal Resistance of High-Power AlInGaN Laser Diodes by a Forward Voltage Relaxation Method

Abstract

An improved method for determining the temperature of a laser diode and the thermal resistance of the main elements of an equivalent thermal circuit based on measuring the transient temperature-sensitive characteristics of the forward voltage at the p–n junction in response to a step-like effect of a heating current pulse was proposed. The individual components and the total thermal resistance of the laser diode were experimentally studied and analyzed. It was found that the main contribution to the total thermal resistance, which was ~7.4 K/W, was made by the laser crystal layer itself from the p–n junction to the lower plane (~2.8 K/W) and the AlN-switching thermally conductive substrate (~2.6 K/W), for which no further reduction paths were visible. It was shown that a continuous mode of operation was realized without significant overheating ΔT < 40 K with the threshold I ≈ 2 A exceeded by six times, generation power P ≈ 2.5 W, efficiency ~30%, and differential quantum output η ≈ 60%.