GaN-based photonic devices operated in ultraviolet (UV) spectrum have drawn much attention in research field. However, the high responsivity and high photo-to-dark ratio cannot be achieved at the same time in traditional UV photodetectors (PDs). Additionally, most of the state-of-art monolithically integrated photonic devices are based on the light emitting diode (LED) structure, which suffer from low responsivity as the light receiver. Fabricating the high performance photonic devices on p-GaN/AlGaN/GaN heterostructure grown on Si wafer is the major task in this thesis.

This thesis introduces the fabrication process and performance of the photonic devices on p-GaN/AlGaN/GaN heterostructure substrate. First, the high performance PDs were fabricated. The high photocurrent was achieved un...[ Read more ]

GaN-based photonic devices operated in ultraviolet (UV) spectrum have drawn much attention in research field. However, the high responsivity and high photo-to-dark ratio cannot be achieved at the same time in traditional UV photodetectors (PDs). Additionally, most of the state-of-art monolithically integrated photonic devices are based on the light emitting diode (LED) structure, which suffer from low responsivity as the light receiver. Fabricating the high performance photonic devices on p-GaN/AlGaN/GaN heterostructure grown on Si wafer is the major task in this thesis.

This thesis introduces the fabrication process and performance of the photonic devices on p-GaN/AlGaN/GaN heterostructure substrate. First, the high performance PDs were fabricated. The high photocurrent was achieved under the UV illumination because of the 2-dimensional electron gas (2DEG) in the AlGaN/GaN interface. With p-GaN on the top of the heterostructure, 2DEG was depleted under dark environment. The low dark current was observed. The PDs demonstrate a high photo-to-dark ratio of ~10⁸, a high UV to visible rejection ratio of ~10⁷ and a high responsivity of 2×10⁴ A/W. Second, the monolithically integrated devices of PD and LED were fabricated on p-GaN/AlGaN/GaN heterostructure substrate. The PDs in previous work act as the light receiver of the integrated device. The forward biased p-GaN/AlGaN/GaN heterostructure diodes act as the light emitter. The photonic signal emitted from LED part was detected by the PDs. With constant bias on PD, the current of the PD can be controlled by the bias on the LED. Benefiting from the high performance PD, the high photo-to-dark ratio of 10⁶ was observed with a positive threshold voltage. Finally, the monolithically integrated devices of LED and HEMT were fabricated on p-GaN/AlGaN/GaN heterostructure substrate. The current in the LED was controlled by the HEMT part. The high current density and uniform light emission were observed in the device.