Compound semiconductors lie at the heart of modern-day information and communications technologies, and of these none is currently more important than gallium nitride and its associated family of alloys. This material system allows the production of sophisticated optical devices (lasers, light-emitting diodes, photodiodes) covering the ultraviolet and visible spectrum for displays, optical data storage and photovoltaics; it enables the development of advanced microwave electronic devices (transistors) for high temperature, high power and high frequency operation. Most of the work currently undertaken with gallium nitride focuses on the basic material itself and the devices that can be made directly from it. Here, in a visionary programme interfacing to a wide range of other materials and disciplines, we seek to explore the unique potential of gallium nitride for 'hybrid and flexible photonics'. These two interrelated themes involve the integration of nitride semiconductor micro/nanostructures and devices with compatible hard and soft materials, which we take to include single crystal diamond, nanocomposites, polymer overlayers and substrates, printable electronics, organic resists, biopolymers, and metal/plasmonic structures. Imagine, for example, hybrid waveguide devices made from gallium nitride and diamond. These could generate and manipulate single photons of light, towards computation and communications systems exploiting the full potential of quantum mechanics, or could enable lasers to be made from diamond via the so-called stimulated Raman process. Imagine, furthermore, the transfer of gallium nitride devices onto flexible substrates and their control via printable electronics. This could facilitate large area micro-displays, and a wide range of instrumentation and communications systems. Imagine the wavelength conversion of gallium nitride emission via nanocomposites and metal-based plasmonic effects, as the basis of multi-gigahertz visible light communications systems. Imagine a range of nanophotonic sources capable of studying fundamental energy transfer processes on a nanoscale and of performing ultra-high resolution photolithography and direct write patterning. All of these capabilities and more can be forseen by the development of hybrid technologies based on gallium nitride. They present tremendous opportunities for UK leadership in fields of science and technology as diverse as nanoscience, lasers and nonlinear optics, quantum information, bioscience and visible light communications.
This grant focussed on combining gallium nitride LED illumination and lighting technology with compatible materials including diamond and polymers, for improved performance and/or enhancing versatility and utility. Waveguide systems were fabricated in GaN and diamond as the basis of new technology for nonlinear optics and quantum technologies; diamond Raman lasers were developed and demonstrated; hybrid GaN/organic and GaN/polymer structures were demonstrated for visible light communications, and novel mechanically flexible nanocomposites and GaN/polymer structures were created. We demonstrated transfer printing technology with nano-positioning accuracy, which opens many new possibilities in mechanical assembly of heterogeneous systems.