Influence of size-reduction on the performances of GaN-based micro-LEDs for display application

Micro-displays based on an array of micro-sized light emitting diodes (µLEDs) are a promising technology for a wide range of applications. In these 2-dimensional arrays, each µLED works as a single pixel of a whole image. In this paper we investigate the effect of size reduction on light emission and efficiency on InGaN/GaN LED devices ranging from 10*10 to 500*500µm². Electroluminescence characterizations together with current–voltage–luminance (IVL) measurements are conducted to study the homogeneity of light emission and correlate with efficiency measurements. The results show a strong size-dependent efficiency. Smaller LEDs exhibit lower maximum efficiency. The light emission homogeneity is shown to be dependent on current densities. At low current density, light emission is homogeneous across the surface of the LED, while inhomogeneity appears at higher current levels. We believe that fabrication process is partly responsible of this phenomenon through a degradation of the electrical injection. Our results are of high importance to understand the properties of µLED arrays. Indeed, such devices would allow the fabrication of very-high brightness emissive micro-displays.