Line beam processing for laser lift-off of GaN from sapphire

Abstract

Gallium nitride (GaN) layers grown on sapphire substrate wafers have been successfully separated using a novel line beam laser lift-off (LLO) approach. The absorption of the 248 nm excimer laser radiation by the GaN through the sapphire wafer results in the formation of metallic gallium and nitrogen gas. The sapphire wafer was easily removable by heating above the gallium melting point. The metallic gallium phase has been inspected via diverse microscopic surface analysis techniques after line beam LLO processing. The measurements indicate that the sapphire separation process using line beam laser scanning has only a marginal impact on the structural quality of the GaN layer. Line beam LLO processing has inherent upscaling advantages over conventional square field LLO. Processing results are evaluated in view of aptness for mass production of high brightness light emitting diodes (HB-LEDs).

Differential interference contrast image of GaN film after 248-nm LLO with line beam (A) and square beam (B).