Electrically driven, polarized, phosphor-free white semipolar (20-21) InGaN light-emitting diodes grown on semipolar bulk GaN substrate.

Abstract

We demonstrate a simple method to fabricate efficient, electrically driven, polarized, and phosphor-free white semipolar (20-21) InGaN light-emitting diodes (LEDs) by adopting a top blue quantum well (QW) and a bottom yellow QW directly grown on (20-21) semipolar bulk GaN substrate. At an injection current of 20 mA, the fabricated 0.1 mm2 size regular LEDs show an output power of 0.9 mW tested on wafer without any backside roughing, a forward voltage of 3.1 V and two emission peaks located at 427 and 560 nm. A high polarization ratio of 0.40 was measured in the semipolar monolithic white LEDs, making them promising candidates for backlighting sources in liquid crystal displays (LCDs). Furthermore, a 3dB modulation bandwidth of 410 MHz in visible light communication (VLC) was obtained in the micro-size LEDs (µLEDs) with a size of 20×20 µm2 and 40×40 µm2, which could overcome the limitation of slow frequency response of yellow phosphor in commercial white LEDs combing blue LEDs and yellow phosphor.