Shockley-Read-Hall and Auger non-radiative recombination in GaN based LEDs: A size effect study

Abstract

GaN-based micro light-emitting diode (μLED) arrays are very promising devices for display applications. In these arrays, each μLED works as a single pixel of a whole image. The electro-optical performance of these μLEDs is an important subject to study. Here, we investigate the influence of LED size on the radiative and non-radiative recombination. The standard ABC model has been widely used to describe the efficiency of GaN based LEDs. Using this model, we extract A, B, and C coefficients for various LED sizes, showing how the competition between radiative and non-radiative recombination processes varies with the LED geometry. Time-resolved photoluminescence allows us to determine coefficient B, related to radiative recombination. Through current-voltage-luminance characterizations, we determine parameters A and C related to Shockley-Read-Hall and Auger recombination. We find that coefficient A is strongly dependent on LED size, indicating a drastic effect of sidewall defects on the performance of LEDs. On the other hand, coefficient C is independent of LED size. This latter result demonstrates that efficiency droop does not depend on LED size.

18‐3: A New Approach for Fabricating High‐Performance MicroLED Displays

“…This specificity can be explained in the light of a typical curve ( Figure 2) showing evolution of External Quantum Efficiency (EQE) as a function of driving current density for a blue InGaN microLED. Evolution of EQE has been investigated thoroughly these last years and recently new models and interpretations have been found, in particular regarding size-dependent effects [9,10]. It is generally admitted that for lower current densities, EQE is impacted by non-radiative recombinations, resulting from defects at the periphery of the devices (Regime 1).…”

11‐2: Micro LEDs Efficiency Targets for Displays

“…1 along with theoretical predictions according to the ABC model. The values of A, B, and C on size and peak wavelength for the InGaN/GaN material system were taken from [12] and [13,14], respectively. It is shown that IQE decreased by ~45% for blue (peak wavelength = 470nm), and by ~70% for green (peak wavelength = 550nm) when the µLED chip size was reduced from 200µm to 5µm.…”

“…Experimental data and theoretical predictions of "planar" InGaN/GaN µLEDs' normalized maximum IQE as a function of µLED size. For theoretical lines, the ABC model was used with model parameters taken from [12][13][14].…”

Green InGaN/GaN based LEDs: high luminance and blue shift

“…Nevertheless, quantum efficiency of µLEDs is yet a challenging subject when dealing with high luminance levels. Besides, µLED size dependence has been thoroughly studied and reported in literature, but mostly for blue color emitting ones 4,5 . A lack of comprehension of size effect is then still to be filled for these green light-emitting diodes dedicated to specific µ-displays applications.…”