The flexible LED fabrication by transferring epitaxial film onto PET

Abstract Flexible AlGaInP-based red light-emitting diodes (LEDs) hold tremendous potential to revolutionize wearable displays. In this work, we propose a method of preparing thin film red LEDs on the polyethylene terephthalate (PET) substrate. We reversed the normal process by bonding the wafer onto the PET and peeling off the GaAs substrate before the device fabrication. Atomic force microscopy (AFM) images showed the root-mean-square (RMS) roughness of 0.155 nm after removing the substrate. Photoluminescence (PL) spectra indicated an 8 nm red shift after bending the thin film, but only a 3 nm raised full width at half maximum (FWHM) from 12 nm to 15 nm. Electroluminescence (EL) spectra exhibited a 10% decreased light output power (LOP) and an increased threshold voltage from 1.5 V to 4 V due to the lack of rapid thermal annealing. This reverse process could save some tedious steps such as massive transfers, which would benefit the micro-LED fabrication. Furthermore, the multi-film stack and multi-LED integrate could realize by several selective etching with this reversed process.