Graphene transparent current-spreading layer on carbon-supported flexible substrates for high-performance GaN LEDs

초록

Flexible GaN light-emitting diodes (LEDs) have attracted considerable research interest owing to their potential applications in wearable displays and optoelectronic integrated devices. Herein, a flexible GaN LED fabricated via laser lift-off is integrated with chemical vapor deposition graphene as a transparent current-spreading (TCS) layer on carbon-supported PET substrates (i.e., Gr-GaN LED). Compared with the GaN LED (without graphene layer), the electroluminescence intensity of the flexible device increased by 35% at an injection current of 50 mA. The photoluminescence (PL) peak intensity is enhanced and the peak wavelength is blue-shifted, corresponding to an increase in output power for Gr-GaN LED. In contrast, the PL peak intensity decreases and the peak wavelength is red-shifted due to reduced output power, was noticed in GaN LED. Graphene carrier transport mechanism was explained. The strain-regulated performance of the device is systematically investigated based on the piezophototronic effect. The strain-regulated polarization characteristics of the flexible device are associated with energy band modulation arising from the anisotropic properties of InGaN/GaN multiple quantum wells. This study provides important insights for the development of flexible GaN LEDs employing highly transparent and flexible graphene TCS layers on mechanically robust carbon-supported PET substrates.

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