20 January 2021

Important developments for visible light communications

A new paper from the Centre for GaN Materials and Devices demonstrates a special approach to on-chip integration of photonics and electronics which has important benefits for visible light communication (VLC) technology.

Optical microscope image of our monolithically integrated device

There is increasing demand for visible light communication (VLC) as a complementary technology to radio frequency (RF) based Wi-Fi and 5G. VLC technology will have applications in a wide range of scenarios where radio frequency emissions are controlled or do not work such as aircraft, hospitals, underwater and hazardous environments. A key component of this technology are III-nitride visible light-emitting diodes (LEDs) which are used as transmitters.

Traditional dry-etching processes used to fabricate III-nitride μLEDs lead to both a substantial reduction in performance and a great challenge to viability at the high injection current density needed for VLC. This concern is significantly enhanced with decreasing μLED dimensions.

Another challenge is achieving the high injection current density and high frequency modulation required for VLC. If a high-electron-mobility transistor (HEMT) is used to supply injection current to the LED a high injection current density can be stably and easily controlled by simply tuning the gate voltage of its HEMT.

In this paper we have addressed both challenges by integrating a μLED and a HEMT on industry-compatible c-plane substrates, where a single μLED with a diameter of 20 μm is controlled by its AlGaN/GaN HEMT. Our monolithically integrated μLED-HEMT device has demonstrated a record modulation bandwidth of 1.2 GHz.

Read the full paper in ACS Applied Electronic Materials.

You can also find out more about our direct epitaxial approach to achieving ultrasmall μLEDs.