Micro-light emitting diodes: effects of size, contact schemes, V pits, and dislocations

In this study, we investigated the effects of size, geometry, contact scheme, and dislocation on the performance of red AlGaInP-based, and green and blue InGaN-based μ-LEDs. For AlGaInP red μ-LEDs, the EQE was characterized as functions of chip size, p-cladding layer thickness, and the number of MQWs. It is shown that a thick p-cladding layer and optimum number of MQWs result in higher EQE. Further, origin for the electrical instability of red μ-LEDs is described in terms of contact schemes. For green InGaN-based μ-LEDs, the optimization of chip size and the presence of V pits is shown to be crucial for the fabrication of high-efficiency μ-LEDs. For blue InGaN-based μ-LEDs, the effects of sidewall conditions, dislocations and optimized passivation on the internal quantum efficiency and light extraction efficiency are described and discussed.