High Bandwidth Freestanding Semipolar (11-22) InGaN/GaN Light-Emitting Diodes

Freestanding semipolar (11-22) indium gallium nitride (InGaN) multiplequantum-well light-emitting diodes (LEDs) emitting at 445 nm have been realized by the use of laser lift-off (LLO) of the LEDs from a 50-mu m-thick GaN layer grown on a patterned (10-12) r-plane sapphire substrate (PSS). The GaN grooves originating from the growth on PSS were removed by chemical mechanical polishing. The 300 mu m x 300 mu m LEDs showed a turn-on voltage of 3.6 V and an output power through the smooth substrate of 0.87 mW at 20 mA. The electroluminescence spectrum of LEDs before and after LLO showed a stronger emission intensity along the [11-23](InGaN/GaN) direction. The polarization anisotropy is independent of the GaN grooves, with a measured value of 0.14. The bandwidth of the LEDs is in excess of 150 MHz at 20 mA, and back-to-back transmission of 300 Mbps is demonstrated, making these devices suitable for visible light communication (VLC) applications.