Optimizing InGaN Micro-LED Efficiency: Investigating the Internal Quantum Efficiency and Ideality Factor Connection

We present a significant enhancement of internal quantum efficiency (IQE) exceeding 90% in InGaN-based Micro-light-emitting diodes (Micro-LEDs) achieved through sidewall passivation using atomic layer deposition (ALD). An intriguing observation is an inverse correlation between the diode ideality factor and IQE; devices boasting over 90% IQE consistently exhibit a diode ideality factor below 1.5. Specifically, for 10-μ m-sized devices, an IQE of 95.6% paired with a remarkably low ideality factor of 1.27 is realized, representing the pinnacle of achievable IQE at room temperature. In addition, enhanced light extraction efficiency (LEE) is observed through a low-refractive-index dielectric layer for passivation, facilitating a large critical angle at the interfaces. However, despite these advancements, the LEE for passivated devices remains at approximately 26%, resulting in an external quantum efficiency (EQE) of 25%. Consequently, our findings strongly advocate further device performance improvements in Micro-LEDs by enhancing LEE, necessitating novel device structures. In addition, we report the groundbreaking verification of the unity ideality factor for radiative recombination current in InGaN-based Micro-LEDs. This achievement is realized through the isolation of the radiative current component from the total current, thus substantiating the legitimacy of employing the Shockley-Read-Hall (SRH) to analyze the electrical characteristics of InGaN Micro-LEDs.