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This study focuses on the heavily Mg-doped GaN in which the passivation effect of hydrogen and the compensation effect of nitrogen vacancies (VN) 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 VN) 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 VN on the surface of heavily Mg-doped GaN. This research could provide crucial insights into the post-growth process of heavily Mg-doped GaN. [ABSTRACT FROM AUTHOR]

In this work, the effects of growth pressure and growth rate on electrical and structural properties of Mg-doped GaN were investigated. It has been shown that enhanced growth rates induced by higher growth pressures may lead to decreased structural and electrical properties of p-type GaN layers. If the growth rate is kept unchanged, higher growth pressures will be beneficial for the quality of Mg-doped GaN due to the enhanced NH overpressure. [ABSTRACT FROM AUTHOR]

In this study, the contact characteristics of p-GaN treated by laser-assisted annealing with different laser fluences were investigated. Based on the two-photon absorption model, a laser treatment on the p-GaN was achieved by utilizing laser with a wavelength of 532 nm. The results showed that specific contact resistance decreased as the laser fluence increased in the low fluence region (<200 mJ/cm2), but deteriorated when the fluence reached to 300 mJ/cm2 or even higher, indicating that laser annealing by 532 nm could greatly affect specific contact resistance. The results of SIMS, photoluminescence spectra, and XPS measurements showed that the enhanced ohmic contact for samples with a low laser injection fluence was attributed to the enhanced aggregation of Mg atoms near the surface and the enhanced activation efficiency of Mg Ga acceptors by the removal of H atoms from Mg–H complexes. For the samples treated with fluence higher than 300 mJ/cm2, the contact characteristics were compromised due to both the accumulation of gallium oxide on the surface which increased the barrier height of metal/GaN and the formation of structural defects. An improved ohmic contact with a specific contact resistance of 2.93 × 10−4 Ω cm2 were demonstrated for p-GaN with the 200 mJ/cm2 laser fluence. 532 nm laser-assisted annealing treatment has great potential for the selective activation of p-GaN and enhancement of GaN/metal contact characteristics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]