In this work, we report on the selective area growth (SAG) of InGaN multiple quantum well (MQW) structures to completely suppress the phenomenon of the Stokes shift in monolithically integrated photonic chips. The original green MQW region is designed as the integrated photodetector (PD), while the SAG blue MQW region acts as the integrated light-emitting diode (LED). The detection spectra of the PD can completely cover the emission spectra of the LED, greatly improving the on-chip optical connection by the complete suppression of the Stokes shift. Thus, the bottleneck of on-chip optical connection based on spectra-tail overlap in integrated photonic chips has been broken. Under the same operating current, the photocurrent of the SAG integrated PD reaches 11.8 μA, while the conventional chip achieves only 0.6 μA. By SAG method, the photo-to-dark current ratio of integrated PD exhibits about two orders of magnitude increase under 0 V bias. Undoubtedly, the SAG technology provides a strategy to further improve the on-chip optical signal transmission efficiency of the MQW structure integrated photonic chips.

We fabricated InGaN/GaN nanorod light emitting diode (LED) on (-201) β-Ga₂O₃ substrate via the SiO₂ nanosphere lithography and dry-etching techniques. The InGaN/GaN nanorod LED grown on β-Ga₂O₃ can effectively suppress quantum confined Stark effect (QCSE) compared to planar LED on account of the strain relaxation. With the enhancement of excitation power density, the photoluminescence (PL) peak shows a large blue-shift for the planar LED, while for the nanorod LED, the peak position shift is small. Furthermore, the simulations also show that the light extraction efficiency (LEE) of the nanorod LED is approximately seven times as high as that of the planar LED. Obviously, the InGaN/GaN/β-Ga₂O₃ nanorod LED is conducive to improving the optical performance relative to planar LED, and the present work may lay the groundwork for future development of the GaN-based vertical light emitting diodes (VLEDs) on β-Ga₂O₃ substrate.

This study focuses on the heavily Mg-doped GaN in which the passivation effect of hydrogen and the compensation effect of nitrogen vacancies (V_N) impede its further development. To investigate those two factors, H ion implantation followed by thermal annealing was performed on the material. The evolution of relevant defects (H and V_N) was revealed, and their distinct behaviors during thermal annealing were compared between different atmospheres (N₂/NH₃). The concentration of H and its associated yellow luminescence (YL) band intensity decrease as the thermal annealing temperature rises, regardless of the atmosphere being N₂ or NH₃. However, during thermal annealing in NH₃, the decrease in H concentration is notably faster compared to N₂. Furthermore, a distinct trend is observed in the behavior of the blue luminescence (BL) band under N₂ and NH₃. Through a comprehensive analysis of surface properties, we deduce that the decomposition of NH₃ during thermal annealing not only promotes the out-diffusion of H ions from the material, but also facilitates the repair of V_N on the surface of heavily Mg-doped GaN. This research could provide crucial insights into the post-growth process of heavily Mg-doped GaN.

The effects of thin Mg back diffusion capping layers on the performance enhancement of InGaN/GaN light emitting diodes (LEDs) with p-InGaN last barrier are investigated experimentally and numerically. By inserting a thin capping layer before the p-InGaN last barrier, the Mg back diffusion effect could be effectively suppressed and the optical performance of LEDs could be enhanced due to the improved hole injection and reduced electron leakage. What is more, the p-InGaN LED with GaN capping layer showed further reduced efficiency droop compared with that with InGaN capping layer as a result of the more uniform hole distribution in active layers.