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p-NiO/n-Ga 2 O 3 heterojunction (HJ) diodes exhibit much larger changes in their properties upon 1.1 MeV proton irradiation than Schottky diodes (SDs) prepared on the same material. In p-NiO/Ga 2 O 3 HJ diodes, the narrow region adjacent to the HJ boundary is found to contain a high density of relatively deep centers with levels near E C -0.17 eV and a depleted region in the immediate vicinity of the HJ boundary. The series resistance of the HJ diodes is slightly higher than for the Schottky diodes and shows a temperature dependence with activation energy ~ 0.12 eV, like the temperature dependence of the NiO film resistivity. Irradiation with 1.1 MeV protons leads to a decrease of the hole concentration in the NiO, with a high carrier removal rate of ~ 1.3 × 10 5  cm −1 and a strong compensation of the interfacial region where the concentration of the E C -0.17 eV centers decreases with a high rate of ~ 7 × 10 3  cm −1 . The combined action of these two effects gives rise to the much stronger increase of the series resistance of the HJ diodes compared to Schottky diodes. The observed differences between the radiation response of the HJs and SDs cannot be credibly attributed to the changes of the density of any of the deep electron and hole traps detected in our experiments.

In this study, the structural and electrical properties of orthorhombic κ-Ga2O3 films prepared using Halide Vapor Phase Epitaxy (HVPE) on AlN/Si and GaN/sapphire templates were studied. For κ-Ga2O3/AlN/Si structures, the formation of two-dimensional hole layers in the Ga2O3 was studied and, based on theoretical calculations, was explained by the impact of the difference in the spontaneous polarizations of κ-Ga2O3 and AlN. Structural studies indicated that in the thickest κ-Ga2O3/GaN/sapphire layer used, the formation of rotational nanodomains was suppressed. For thick (23 μm and 86 μm) κ-Ga2O3 films grown on GaN/sapphire, the good rectifying characteristics of Ni Schottky diodes were observed. In addition, deep trap spectra and electron beam-induced current measurements were performed for the first time in this polytype. These experiments show that the uppermost 2 µm layer of the grown films contains a high density of rather deep electron traps near Ec − 0.3 eV and Ec − 0.7 eV, whose presence results in the relatively high series resistance of the structures. The diffusion length of the excess charge carriers was measured for the first time in κ-Ga2O3. The film with the greatest thickness of 86 μm was irradiated with protons and the carrier removal rate was about 10 cm−1, which is considerably lower than that for β-Ga2O3.

In this study, the results of hydrogen plasma treatments of β-Ga2O3, α-Ga2O3, κ-Ga2O3 and γ-Ga2O3 polymorphs are analyzed. For all polymorphs, the results strongly suggest an interplay between donor-like hydrogen configurations and acceptor complexes formed by hydrogen with gallium vacancies. A strong anisotropy of hydrogen plasma effects in the most thermodynamically stable β-Ga2O3 are explained by its low-symmetry monoclinic crystal structure. For the metastable, α-, κ- and γ-polymorphs, it is shown that the net result of hydrogenation is often a strong increase in the density of centers supplying electrons in the near-surface regions. These centers are responsible for prominent, persistent photocapacitance and photocurrent effects.

We demonstrate high-performance InGaN/GaN blue light emitting diodes (LEDs) embedded with an air-void layer produced by a dry-etch of nano-pillars in an n-GaN layer grown on patterned sapphire substrate (PSS), filling the space between nano-pillars with SiO2 nano-particles (NPs) and subsequent epitaxial overgrowth. The structure exhibits enhanced output power compared to similarly grown reference conventional LED without the air-void layer. This change in growth procedure contributes to the increase of internal quantum efficiency (IQE) and light extraction efficiency (LEE) resulting in a 13.5% increase of light output. LEE is 2 times more affected than IQE in the modified structure. Simulation demonstrates that the main effect causing the LEE changes is due to the emitted light being confined within the upper space above the air-void layer and thus enhancing the light scattering by the SiO2 NPs and preferential light via front surface.

In this study, the results of hydrogen plasma treatments of β-Ga[sub.2]O[sub.3], α-Ga[sub.2]O[sub.3], κ-Ga[sub.2]O[sub.3] and γ-Ga[sub.2]O[sub.3] polymorphs are analyzed. For all polymorphs, the results strongly suggest an interplay between donor-like hydrogen configurations and acceptor complexes formed by hydrogen with gallium vacancies. A strong anisotropy of hydrogen plasma effects in the most thermodynamically stable β-Ga[sub.2]O[sub.3] are explained by its low-symmetry monoclinic crystal structure. For the metastable, α-, κ- and γ-polymorphs, it is shown that the net result of hydrogenation is often a strong increase in the density of centers supplying electrons in the near-surface regions. These centers are responsible for prominent, persistent photocapacitance and photocurrent effects.

Mesoporous silver nanoparticles were easily synthesized through the bulk reduction of crystalline silver(I) oxide and used for the preparation of highly porous surface-enhanced Raman scattering (SERS)-active substrates. An analogous procedure was successfully performed for the production of mesoporous silver films by chemical reduction of oxidized silver films. The sponge-like silver blocks with high surface area and the in-situ-prepared mesoporous silver films are efficient as both analyte adsorbents and Raman signal enhancement mediators. The efficiency of silver reduction was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The developed substrates were applied for SERS detection of rhodamine 6G (enhancement factor of about 1–5 × 10 5 ) and an anti-ischemic mildronate drug (meldonium; enhancement factor of ≈10 2 ) that is known for its ability to increase the endurance performance of athletes.

In this study, the structural and electrical properties of orthorhombic κ-Ga O films prepared using Halide Vapor Phase Epitaxy (HVPE) on AlN/Si and GaN/sapphire templates were studied. For κ-Ga O /AlN/Si structures, the formation of two-dimensional hole layers in the Ga O was studied and, based on theoretical calculations, was explained by the impact of the difference in the spontaneous polarizations of κ-Ga O and AlN. Structural studies indicated that in the thickest κ-Ga O /GaN/sapphire layer used, the formation of rotational nanodomains was suppressed. For thick (23 μm and 86 μm) κ-Ga O films grown on GaN/sapphire, the good rectifying characteristics of Ni Schottky diodes were observed. In addition, deep trap spectra and electron beam-induced current measurements were performed for the first time in this polytype. These experiments show that the uppermost 2 µm layer of the grown films contains a high density of rather deep electron traps near E - 0.3 eV and E - 0.7 eV, whose presence results in the relatively high series resistance of the structures. The diffusion length of the excess charge carriers was measured for the first time in κ-Ga O . The film with the greatest thickness of 86 μm was irradiated with protons and the carrier removal rate was about 10 cm , which is considerably lower than that for β-Ga O .

In this study, the structural and electrical properties of orthorhombic κ-Ga[sub.2]O[sub.3] films prepared using Halide Vapor Phase Epitaxy (HVPE) on AlN/Si and GaN/sapphire templates were studied. For κ-Ga[sub.2]O[sub.3]/AlN/Si structures, the formation of two-dimensional hole layers in the Ga[sub.2]O[sub.3] was studied and, based on theoretical calculations, was explained by the impact of the difference in the spontaneous polarizations of κ-Ga[sub.2]O[sub.3] and AlN. Structural studies indicated that in the thickest κ-Ga[sub.2]O[sub.3]/GaN/sapphire layer used, the formation of rotational nanodomains was suppressed. For thick (23 μm and 86 μm) κ-Ga[sub.2]O[sub.3] films grown on GaN/sapphire, the good rectifying characteristics of Ni Schottky diodes were observed. In addition, deep trap spectra and electron beam-induced current measurements were performed for the first time in this polytype. These experiments show that the uppermost 2 µm layer of the grown films contains a high density of rather deep electron traps near E[sub.c] − 0.3 eV and E[sub.c] − 0.7 eV, whose presence results in the relatively high series resistance of the structures. The diffusion length of the excess charge carriers was measured for the first time in κ-Ga[sub.2]O[sub.3]. The film with the greatest thickness of 86 μm was irradiated with protons and the carrier removal rate was about 10 cm[sup.−1], which is considerably lower than that for β-Ga[sub.2]O[sub.3].

p-NiO/n-Ga O heterojunction (HJ) diodes exhibit much larger changes in their properties upon 1.1 MeV proton irradiation than Schottky diodes (SDs) prepared on the same material. In p-NiO/Ga O HJ diodes, the narrow region adjacent to the HJ boundary is found to contain a high density of relatively deep centers with levels near E -0.17 eV and a depleted region in the immediate vicinity of the HJ boundary. The series resistance of the HJ diodes is slightly higher than for the Schottky diodes and shows a temperature dependence with activation energy ~ 0.12 eV, like the temperature dependence of the NiO film resistivity. Irradiation with 1.1 MeV protons leads to a decrease of the hole concentration in the NiO, with a high carrier removal rate of ~ 1.3 × 10  cm and a strong compensation of the interfacial region where the concentration of the E -0.17 eV centers decreases with a high rate of ~ 7 × 10  cm . The combined action of these two effects gives rise to the much stronger increase of the series resistance of the HJ diodes compared to Schottky diodes. The observed differences between the radiation response of the HJs and SDs cannot be credibly attributed to the changes of the density of any of the deep electron and hole traps detected in our experiments.

This chapter contains sections titled: Introduction Fundamental Studies of Radiation Defects in GaN and Related Materials Radiation Effects in Other III‐Nitrides Radiation Effects in GaN Schottky Diodes, in AlGaN/GaN and GaN/InGaN Heterojunctions and Quantum Wells Radiation Effects in GaN‐Based Devices Prospects of Radiation Technology for GaN Summary and Conclusions Acknowledgments