Physical mechanisms on the size-effect in GaN-based Micro-LEDs

In this work, physical mechanisms on the size-effect in GaN-based micro-LEDs have been thoroughly investigated by device modelling and TCAD simulations. The radiative recombination rate of micro-LEDs is investigated under different sidewall trap density values, energy levels and LED sizes by TCAD simulations. It is found that the total radiative recombination decreases with the downscaling of LED size. This size-effect is attributed to the depletion effect of sidewall traps and the current injection efficiency drop due to lateral current dispersion resulted from carriers being captured by sidewall traps, both of which are related to sidewall traps induced by dry-etching process. It is concluded that reduced sidewall trap density and a deeper energy level of acceptor-like trap are helpful to suppress the size effect. The modelling achieves good agreement with experimental data from literatures. Besides, a novel C-shaped anode structure is proposed to suppress the size effect by counteracting the transverse electric field. To the best of our knowledge, this is the first time such a physical model is derived to provide design and process guidelines for GaN-based micro-LEDs.