Photonic integration in GaN membranes on Silicon

by Dr. Hoi Wai Choi
Jan 14, 2016

Summary of the NSFC/RGC project (Dr. H W Choi)

Project Reference: N_HKU710/15
HK Principal Investigator: Dr. Hoi Wai Choi (The University of Hong Kong)
Mainland Principal Investigator: Professor Yongjin Wang (Nanjing University of Posts and Telecommunications)

Half century since the invention of the visible light-emitting diode (LED), the technology has blossomed from a minuscule light emitter to present-day powerful illuminators, driven by explosive developments in material and processing technologies, including but not limited to advanced epitaxy of complex quantum structures, nanotechnology-enabled devices and sophisticated chip packaging  techniques to accommodate the needs of such avant-garde devices.  Today LEDs are part of everyday lives, appearing as traffic lights, LCD backlights, desktop lamps, handheld torches just to name a few.  Of course LEDs are not limited to domestic uses; devices of specific wavelengths are adopted in professional products such as phototherapy, biotechnology, medical imaging, and microscopy owing to their distinct optical emission characteristics not found from any other light sources.  However, there is one application of LEDs that have not been fully explored: as emitters in photonic systems.  Such roles have conventionally been fulfilled by laser sources due to issues of optical coupling between LEDs and other photonic components. 

The photonic circuit concept has been introduced in recent years, whereby different photonic components of different functions are monolithically integrated onto a single chip. In this ambitious yet fully realizable project we attempt to integrate LEDs with waveguides and photodetectors to build a highly-integrated photonic system to perform functionalities including optical communications, based on the GaN-on-Si platform.  This is possible due to the fact that the GaN materials play the three functions of light emission, transmission and detector simultaneously, and most importantly, equally well.  At the same time, the Si substrate can readily be removed for the formation of highly-confining waveguides.  Therefore, the outcomes of this project will pave the way towards next-generation photonic chips based on the GaN materials.