Low-Voltage, High-Brightness Silicon Micro-LEDs for CMOS Photonics

Silicon photonics realized in CMOS processes has transformed computing, communications, sensing, and imaging. Although silicon is an indirect bandgap material prohibiting efficient light generation, considerable work has been conducted in the field of silicon p-n junctions emitting broadband visible light when operating in the high-voltage reverse breakdown avalanching mode. Here, we demonstrate high-brightness near-infrared (NIR) light emission for forward-biased silicon micro-light emitting diodes (micro-LEDs) realized in an open-foundry microelectronic CMOS process—55 BCDLite—with zero modification. Under room-temperature continuous-wave operation, the external light emission intensity of over 40 mW/cm
$^{{2}}$
at a central wavelength of 1020 nm is achieved for a 4-
$\mu \text {m}$
-diameter device at below 2.5 V. This is realized by adopting a deep vertical junction with guard ring designs that ensure carrier transport away from the device surface and material interfaces where nonradiative recombination usually dominates. Here, we also demonstrate a complete chip-to-chip communication link using only standard multimode fiber and monolithically integrated CMOS micro-LEDs and detectors.