Martin Straßburg

Temperature-dependent recombination coefficients in InGaN light-emitting diodes: Hole localization, Auger processes, and the green gap

We obtain temperature-dependent recombination coefficients by measuring the quantum efficiency and differential carrier lifetimes in the state-of-the-art InGaN light-emitting diodes. This allows us to gain insight into the physical processes limiting the quantum efficiency of such devices. In the green spectral range, the efficiency deteriorates, which we assign to a combination of diminishing electron-hole wave function overlap and enhanced Auger processes, while a significant reduction in material quality with increased In content can be precluded. Here, we analyze and quantify the entire balance of all loss mechanisms and highlight the particular role of hole localization.

Determination of recombination coefficients in InGaN quantum-well light-emitting diodes by small-signal time-resolved photoluminescence

We suggest a novel technique for the evaluation of the recombination coefficients corresponding to Shockley–Read–Hall, radiative, and Auger recombination that occur in InGaN/GaN-based light-emitting diodes (LEDs). This technique combines the measurement of the LED efficiency as a function of LED drive current with a small-signal time-resolved photoluminescence measurement of the differential carrier life time (DLT). Using the relationships between the efficiency and DLT following from the empirical ABC-model, one can evaluate all three recombination coefficients. The suggested technique is applied to a number of single- and multiple-quantum well LEDs to gain a deeper insight into the mechanisms ultimately limiting their efficiency.