Micro-LED transfer via electrochemical etch

University of California Santa Barbara (UCSB) in the USA claims the first demonstration of fully functional vertical micro-scale light-emitting diodes (micro-LEDs), spanning device dimensions down to 3μm, transferred via selective electrochemical etching and direct wafer bonding [Yifan Yao et al, Appl. Phys. Lett., v128, p121103, 2026].

The team comments: “This proof-of-concept demonstration establishes a low-damage, high-throughput pathway for mass transfer of III-nitride devices, enabling scalable heterogeneous integration with various functional platforms for micro-displays, optical communications, and sensing systems.”

Although indium gallium nitride (InGaN) LEDs can be grown on silicon, the performance of such devices tends to be impacted by defects generated by the lattice and thermal mismatch of the respective materials. Silicon platforms are desired for their ability to produce low-cost, large-area electronic drive circuitry, not to mention photonic integrated circuit (PIC) structures, incorporating waveguides and so on.

The alternative method is to transfer reduced defect LEDs produced on more suitable substrates such as bulk or free-standing GaN, or lower-cost sapphire, which is closer to GaN in lattice structural terms than silicon.

A typical method of separation of LEDs from the sapphire growth substrate is laser lift-off (LLO), which involves concentrated laser light thermally decomposing GaN near the substrate, allowing removal and transfer.

The team comments: “Although widely adopted in industry, LLO involves high interfacial temperatures that often exceed the growth temperature of the active region and therefore can induce crystal damage or cracking during the release process and is fundamentally limited to substrates that are transparent to the ultraviolet laser.”

Photo descriptions: Figure 1. (a) Micro-LED transfer process scheme. (b) Epitaxial structure. Differential interference contrast microscopy false-colored images: (c) before EC etching and bonding (from p-side) and (d) after transfer to silicon carrier substrate (from n-side).

Tags: microLED

Visit: https://doi.org/10.1063/5.0327220

The author Mike Cooke is a freelance technology journalist who has worked in the semiconductor and advanced technology sectors since 1997.