Monolithically GaN-Based Optocoupler With Chip Scaling

This study proposed a GaN-based optocoupler with monolithic integration. While commercial photodiode (PD) optocouplers have at least two coupled chips, this work monolithically integrated a light-emitting diode (LED) and a PD on a sapphire substrate as a single packaged chip. A typical bare die (BD) was successfully fabricated on a sapphire substrate with a size of $1.0\times1.6$ mm. After it was encapsulated with filled silicone and TiO2 nanoparticles, the optical signal transmission was carried out in a thin sapphire substrate with a microscale path of radiation, greatly reducing light loss. The measurement results revealed that the proposed chip, housed in a silicone compound sealant, produced $10 ~\mu \text{A}$ of photocurrent when a 10-mA current was applied to the emitting element. As a result, a great current transfer ratio (CTR) of 0.1% was achieved. These results indicate that the proposed device can provide a more efficient solution for the manufacturing and compact packaging of optocoupler components.