Uniting GaN Electronics and Photonics on A Single Chip

The bandgap energies of the group III-V semiconductor gallium nitride (GaN) and its alloys cover emission wavelengths ranging from the ultraviolet to the visible. Concurrently, GaN has enabled high performance transistors to provide attractive solutions in the high voltage and high frequency regimes. Both GaN optoelectronics and electronics have been successfully developed, and the two technologies are often dependent on each other in many real-life applications. In the simplest case, both the GaN light-emitting diode (LED) and photodiode have to be driven or amplified by transistor-based circuits. However, these circuits are separately made on the Si platform. What if GaN optoelectronics and electronics can be integrated onto the same platform? That would result in significant reduction in material costs, processing costs and packaging costs. At the same time, the performance of the monolithically integrated system will be significantly improved, due to reduced resistances and parasitic capacitances. In view of such prospects, we propose and characterize monolithically integrated GaN metal-oxide-semiconductor field effect transistors (MOSFETs), transmitter, waveguide, and receiver, which are fabricated onto a conventional InGaN/GaN LED wafer without involving re-growth or post-growth doping (diffusion or ion implantation). The capability of integrating optoelectronics (transmitter, waveguide, receiver) with MOSFETs would inevitably open up new horizons for the GaN platform.