Phosphor-free microLEDs with ultrafast and broadband features for visible light communications

Abstract

Modulation bandwidth and the emission region are essential features for the widespread use of visible light communications (VLC). This paper addresses the contradictory requirements to achieve broadband and proposes ultrafast, asymmetric pyramids grown on adjacent deep concave holes via lateral overgrowth. Multicolor emission with an emission region between 420 nm and 600 nm is obtained by controlling the growth rate at different positions on the same face, which also can provide multiple subcarrier frequency points for the employment of wavelength division multiplexing technology. The spontaneous emission rate distinction is narrowed by lowering the number of the crystal plane, ensuring a high modulation bandwidth over broadband. More importantly, the residual stress and dislocation density were minimized by employing a patterned substrate, and lateral overgrowth resulted in a further enhancement of the recombination rate. Finally, the total modulation bandwidth of multiple subcarriers of the asymmetric pyramids is beyond GHz. These ultrafast, multicolor microLEDs are viable for application in VLC systems and may also enable applications for intelligent lighting and display.