Monolithically Integrated UV Photoelectric Switch Based on GaN-on-Silicon Platform

We report a monolithically integrated ultraviolet (UV) photoelectric switch based on a GaN-on-silicon platform for the first time. The novel integrated switch consists of a U-shaped trench metal-oxide-semiconductor field effect transistor (UMOSFET), an InGaN/GaN multiple quantum wells (MQW) UV photodiode (PD), and a thin-film resistor. A common blue light-emitting diode epi wafer is adopted to design and fabricate the switch without an extra epitaxy growth or ion implantation process, which greatly simplifies the fabrication. The backside of the chip is designed to receive the incident light. The shielding of the silicon substrate indicates the UMOSFET and thin-film resistor are immune to interference from the incident light, except for the PD. Under UV illumination, the induced photocurrent in the MQW PD is converted into a voltage by the thin-film resistor and is used to drive the UMOSFET for output. The measured results indicate that the response speed of the photoelectric switch with 21 Hz cut-off frequency is mainly limited by the fall time of PD photocurrent.