A novel vacuum epitaxial lift-off (VELO) process for separation of hard GaAs substrate/carrier systems for a more green semiconductor LED production

Abstract This study reports on a novel vacuum epitaxial lift-off (VELO) process to reuse the GaAs substrates in light-emitting diode (LED) production. The method is based on an epitaxial lift-off technique, whose application is however limited to flexible wafers, as gaseous reaction products (e.g. AsH 3 ) formed during the etching of AlAs with hydrofluoric acid are trapped within the wafer stack. In the developed VELO process, an applied vacuum of ∼ 5000 Pa to the bonded wafer stack removes such detrimental reaction gases, allowing a separation of hard substrate/carrier systems. The VELO process is evaluated with a state-of-the-art thin-film light-emitting diode (TF-LED) phosphide-based epitaxial structure with a buried AlAs sacrificial layer and a simplified LED chip construction at 4-in. wafer level. Characterization of the so-processed LEDs using high-resolution x-ray diffraction, μ -photoluminescence and electrical testing reveal that the VELO TF-LEDs show a comparable performance like to released chips by using conventional grinding/polishing and etching of the GaAs substrate. As our VELO process is non-destructive to the substrate, the GaAs wafers can be reused, enabling lower costs for LED production and reduced toxic waste to establish a green semiconductor production.