InGaN-based green micro-LED efficiency enhancement by hydrogen passivation of the p-GaN sidewall

Abstract

We investigated the effect of the sidewall passivation by hydrogen plasma on the InGaN green micro-LED performance. Hydrogen passivation deactivates the surface region of p-GaN around the perimeter of the device mesa. Thus, hole injection is suppressed in this region, where etching-caused material degradation results in leakage current, decreasing device efficiency. We have confirmed the hydrogen passivation effect on LED square pixels with sizes of 20 µm and 100 µm. For smaller LEDs, the reverse leakage current has reduced more than tenfold, and the external quantum efficiency of LEDs was enhanced 1.4-times due to the suppression of the non-radiative recombination.

Impact of sidewall conditions on internal quantum efficiency and light extraction efficiency of micro-LEDs

“…Similar result of suppressing YL band by sol-gel SiO2 was reported elsewhere [16]. The most important thing in the performance of µLEDs is the sidewall condition [34][35][36][37][38][39][40]. Except for special cases, such as semipolar and nonpolar GaN LEDs, most GaN-based LED wafers are grown on c-plane sapphire, and hence the sidewall should have a non-polar surface such as m-plane orientation (Figure 2).…”

Impact of Sidewall Conditions on Internal Quantum Efficiency and Light Extraction Efficiency of Micro‐LEDs

“…Similar result of suppressing YL band by sol-gel SiO2 was reported elsewhere [16]. The most important thing in the performance of µLEDs is the sidewall condition [34][35][36][37][38][39][40]. Except for special cases, such as semipolar and nonpolar GaN LEDs, most GaN-based LED wafers are grown on c-plane sapphire, and hence the sidewall should have a non-polar surface such as m-plane orientation (Figure 2).…”

“…The most important thing in the performance of µLEDs is the sidewall condition. [36][37][38][39][40][41][42] Except for special cases, such as semipolar and nonpolar GaN LEDs, most GaN-based LED wafers are grown on c-plane sapphire, and hence the sidewall should have a nonpolar surface such as m-plane orientation (Figure 2). X-ray photoelectron spectroscopy (XPS) analysis is suitable for confirming the surface states.…”

An Ultrahigh Efficiency Excitonic Micro-LED

“…External quantum efficiency for some previously reported InGaN-based green and red LEDs with different active region areas, showing a significant reduction in efficiency with reducing sizes. − …”

“…For future virtual/augmented reality displays, visible LEDs with lateral dimensions as small as one micrometer, i.e., surface area nearly one million times smaller than conventional broad area devices, are required . Plotted in Figure , the external quantum efficiency (EQE) of such small size InGaN-based devices is often one to two orders of magnitude lower than conventional broad area LEDs, especially for devices operating in the green and red spectra. − The underlying challenges have been extensively studied, primarily the consequences of etch induced damage, including degraded p-type contact, and significantly enhanced nonradiative surface recombination. − Various approaches have been employed to enhance the efficiency of micro and nanoscale quantum well LEDs but with very limited success. The integration of individual micro-LED devices into a display is also a major hurdle due to the sheer number of devices required and the precision needed in their placing …”