Aging characteristics of blue InGaN micro-light emitting diodes at an extremely high current density of 3.5 kA cm⁻²

Abstract

The aging characteristics of blue InGaN micro-light emitting diodes (micro-LEDs) with different sizes have been studied at an extremely high current density 3.5 kA/cm 2 for emerging micro-LED applications including visible light communication, micro-LED pumped organic lasers and optogenetics. The light output power of micro-LEDs first increases and then decreases due to the competition of Mg activation in p-GaN layer and defect generation in the active region. The smaller micro-LEDs show less light output power degradation compared with larger micro-LEDs, which is attributed to the lower junction temperature of smaller micro-LEDs. It is found that the high current density without additional junction temperature cannot induce significant micro-LED degradation at room temperature but the combination of the high current density and high junction temperature leads to strong degradation. Furthermore, the cluster LEDs, composed of a micro-LED array, have been developed with both high light output power and less light output degradation for micro-LED applications in solid state lighting and visible light communication.

Characteristics of Micro‐Size Light‐Emitting Diode for Illumination and Visible Light Communication

“…Due to its ability to sustain high injected current density and its small capacitance, the micro‐size LED can easily reach a high modulation bandwidth in the order of several hundred MHz and is a promising signal emitter in VLC system . However, although the higher current density is beneficial to the higher modulation bandwidth, it leads to worse aging characteristics due to the self‐heating effect . For example, the light‐output power of the 300 × 300 µm 2 broad‐area LED drops about 5.5% after 96 h under the current density of 100 A cm −2 , while the power drops about 29% after 2 h under the current density of 200 A cm −2 .…”

“…However, although the higher current density is beneficial to the higher modulation bandwidth, it leads to worse aging characteristics due to the self‐heating effect . For example, the light‐output power of the 300 × 300 µm 2 broad‐area LED drops about 5.5% after 96 h under the current density of 100 A cm −2 , while the power drops about 29% after 2 h under the current density of 200 A cm −2 . In addition, the micro‐size LED only gives few luminous fluxes because of the tiny area of active layer.…”

“…The light‐output power in the order of milliwatt may be adequate for the photoelectric detectors as a signal emitter, but the corresponding luminous flux is not enough for the human eyes as an illumination source. Thus, the arrayed micro‐pixels are adopted to raise the total luminous flux …”

Active tracking system for visible light communication using a GaN-based micro-LED and NRZ-OOK

“…With the bias current higher than 61 mA, the bandwidth keeps constant around 160 MHz. Higher current causes more self-heating to the micro-LED, thus higher junction temperature degrades the micro-LED's lifetime and reliability dramatically [16][17][18][19]. Therefore, we chose 40.…”

55-2:Invited Paper: ILED Displays: Next Generation Display Technology

“…Shown in Figure 3 is an example of a 20μm diameter μLED which is driven with a current of 400μA equivalent to a current density of greater than 100A/cm 2 . μLED devices have been shown capable of handling current densities of 3.5kA/cm 2 with no detrimental ageing effects, as the small volume and proportionally large surface area enables efficient heat dissipation [3].…”