Wafer-scale epitaxial lift-off of GaN using bandgap-selective photoenhanced wet etching

An epitaxial lift-off (ELO) process for GaN materials has been demonstrated using bandgap-selective photoenhanced wet etching of an InGaN release layer. This process has been applied to GaN layers grown on sapphire as well as native GaN substrates using a perforation technique to scale the process up to wafers of arbitrary size. The process has the advantage of leveraging conventional MOCVD growth to form the release layer, with minimal degradation of films grown on top of the release layer. The ELO process is non-destructive and can enable cost reduction through reuse of the native GaN substrate after ELO. The GaN films have been characterized before and after ELO using AFM, SEM, XRD, TEM and by fabricating Schottky barrier diodes. The performance of Schottky diodes fabricated on GaN-on-sapphire structures was found to improve after ELO. Potential applications for this technology include GaN power and optoelectronic devices as well as flexible electronics. Shown is a 5-micron-thick GaN epitaxial film released from a 4-inch sapphire substrate using perforations on a 1-mm pitch. The yellow luminescence of the nitrogen face of the released film is visible under ultraviolet illumination.