Optical and electrical characterizations of micro-LEDs grown on lower defect density epitaxial layers

Abstract

We have fabricated μLEDs of mesa sizes 10 × 10 and 15 × 15 μm2 on native (2021¯) semipolar substrates and on epitaxial lateral overgrown (ELO) wings of the (2021¯) substrate. The ELO μLEDs exhibited very low leakage current (less than 10−10 A) under forward bias (V < 2 V) and at reverse bias voltages, which was a reduction in several orders of magnitude when compared with planar μLEDs under the same fabrication and sidewall passivation scheme. Electrical characterization revealed that the mesa sidewall is less damaged in plasma dry etching in the ELO μLEDs due to a lower material defect density than the planar μLEDs. Moreover, the ELO μLEDs showed improved optical performance over the planar μLEDs.

Technology and Applications of Micro-LEDs: Their Characteristics, Fabrication, Advancement, and Challenges

“…The electrical, optical, and thermal characteristics of μLEDs mainly depend on the epitaxial materials, device pixel geometry, and packaging. − Zhang et al comprehensively investigated the performance of μLEDs according to different shapes, sizes, and some drastic conditions. They concluded that the geometric shape of the device influences the current uniformity.…”

Semipolar {202¯1} GaN Edge-Emitting Laser Diode on Epitaxial Lateral Overgrown Wing

“…However, high substrate cost, supply, and size limitations preclude the full realization of the market potential of semi-and non-polar LDs. To address these limitations, we propose a new approach combining ELO and a robust peeling method for semi-and non-polar optical devices ( [21][22][23][24][25][26][27][28], patent applications (i)-(xxx)). The feasibility of this new approach was studied for various devices such as non-polar LDs [21], n-side-distributed Bragg reflectors [23], and semipolar µLEDs [24].…”

“…To address these limitations, we propose a new approach combining ELO and a robust peeling method for semi-and non-polar optical devices ( [21][22][23][24][25][26][27][28], patent applications (i)-(xxx)). The feasibility of this new approach was studied for various devices such as non-polar LDs [21], n-side-distributed Bragg reflectors [23], and semipolar µLEDs [24]. Briefly, the process by which we may lower the commercialization hurdle consists of (1) utilizing ELO on expensive, free-standing GaN substrates for optical device fabrication, (2) removing the devices from the substrate, and (3) reusing the expensive substrate.…”

“…It is therefore expected that an extension of the ELO LD and the removal of the workflow to semipolar GaN substrates will meet this need. Moreover, coupled with the wider wings and reduced defect densities achievable with such planes [22,24], semipolar ELO may also enhance device lifetimes and lower the threshold current of ELO-templated laser ridges [31]. We earlier reported reduced threading dislocations on the ELO wings of {2021} crystalline plane [24].…”

“…Moreover, coupled with the wider wings and reduced defect densities achievable with such planes [22,24], semipolar ELO may also enhance device lifetimes and lower the threshold current of ELO-templated laser ridges [31]. We earlier reported reduced threading dislocations on the ELO wings of {2021} crystalline plane [24]. As such, the following study features laser diodes formed on the wings of the {2021} crystalline plane, which allows for indium incorporation at higher temperatures for higher crystal quality growth of the quantum wells, assuming a similar reduction in threading dislocations.…”