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Abstract This work reports high structural quality and exceptional electrical transport properties of homoepitaxialβ‐Ga₂O₃thin films grown by Metal–Organic Chemical Vapor Deposition (MOCVD) on (010)‐ and (–201)‐oriented substrates. (010)β‐Ga₂O₃samples exhibit mobility of up to 69.4 cm² (V·s)⁻¹and stable hole concentrations ≈2.4 × 10¹⁷ cm⁻³from 370 to 700 K. Structural and morphological studies, including XRD, AFM, and STEM, confirm high epitaxial quality, absence of extended defects and minimal strain. (–201)β‐Ga₂O₃layer, which is simultaneously grown, exhibits typicalp‐Ga₂O₃behavior with observed deep level defects. The hole mobility ranging from 26 to 36 cm² V⁻¹·s⁻¹is measured between 420 and 700 K. Comparison of (010) and (–201) orientations reveals distinct anisotropic electrical properties. The findings emphasize the free motion of holes inβ‐Ga₂O₃and the critical role of crystallographic orientation. 

Abstract Lateral Schottky or heterojunction rectifiers were irradiated with 10 MeV protons and neutrons. For proton irradiation, the forward current of both types of rectifiers decreased by approximately an order of magnitude, with a corresponding increase in on-state resistance. The resultant on/off ratio improved after irradiation because of the larger decrease in reverse current compared to forward current. Both types of rectifiers displayed a shift in forward current and RON curves to lower voltages after irradiation. This could be due to defects created by neutron irradiation introducing deep energy levels within the bandgap of AlN. These deep levels can trap charge carriers, reducing their mobility and increasing the on-state resistance. Transmission electron microscopy showed disorder created at the AlN/NiO interface by neutron irradiation. TCAD simulation was used to study the effects of irradiation with both protons and neutrons. The results confirmed that the irradiation caused a significant reduction in electron concentration and a small increase in the recombination rate. Neutron irradiation can also introduce interface states at the metal or oxide-semiconductor junction of the rectifier. These interface states can modify the effective Schottky barrier height, affecting the forward voltage drop and on-state resistance. 

As a viable alternative to the challenging fabrication of robust β-Ga2O3 p–n homojunctions, this study investigates the variable-temperature photocurrent of p-NiO/n-Ga2O3 heterojunction photodiodes under zero-bias conditions. The device's built-in electric field is utilized to achieve efficient separation of non-equilibrium photogenerated carriers. To support the experimental findings, computer simulations of the electric field distribution at the heterointerface were performed and correlated with experimental current–voltage and capacitance–voltage measurements. The photocurrent measurements confirm the narrowing of the n-Ga2O3 bandgap with increasing temperature, consistent with predictions from the Varshni equation. The observed decrease in photocurrent amplitude at lower temperatures is attributed to bandgap widening, which results in a smaller number of non-equilibrium carriers generated by the excitation wavelength. 

This study investigates minority electron diffusion length and carrier recombination phenomena in p-type 300 nm-thick Ga2O3 films homoepitaxially grown over a (001) tin-doped β-Ga2O3 conductive substrate. This research is novel due to its systematic and near-simultaneous measurements in the top layer of a p-Ga2O3/n-Ga2O3 structure using independent electron beam-induced current and cathodoluminescence techniques. Previous work primarily focused on heteroepitaxial architectures or gallium oxide grown over insulating substrates of the same material. In this work, the activation energies related to point defects in gallium oxide were extracted from temperature-dependent incremental electron beam irradiation experiments to gain insight into the defect landscape and its influence on minority carrier transport and recombination dynamics. 

Gallium oxide (Ga2O3) exists in different polymorphic forms, including the trigonal (α), monoclinic (β), cubic (γ), and orthorhombic (κ) phases, each exhibiting distinct structural and electronic properties. Among these, β-Ga2O3 is the most thermodynamically stable and widely studied for high-power electronics applications due to its ability to be grown as high-quality bulk crystals. However, metastable phases such as α-, γ-, and κ-Ga2O3 offer unique properties, including wider bandgap or strong polarization and ferroelectric characteristics, making them attractive for specialized applications. This paper summarizes the radiation hardness of these polymorphs by analyzing the reported changes in minority carrier diffusion length (LD) and carrier removal rates under various irradiation conditions, including protons, neutrons, alpha particles, and gamma rays. β-Ga2O3 demonstrates high radiation tolerance with LD reductions correlated to the introduction of electron traps (E2*, E3, and E4) and gallium–oxygen vacancy complexes (VGa–VO). α-Ga2O3 exhibits slightly better radiation hardness similar to κ-Ga2O3, which also shows minimal LD changes postirradiation, likely due to suppressed defect migration. γ-Ga2O3 is the least thermodynamically stable, but surprisingly is not susceptible to radiation-induced damage, and is stabilized under Ga-deficient conditions. The study highlights the role of polymorph-specific defect dynamics, doping concentrations, and nonuniform electrical properties in determining radiation hardness. We also discuss the effect of radiation exposure on the use of NiO/Ga2O3 heterojunction rectifiers that provide superior electrical performance relative to Schottky rectifiers. The presence of NiO does change some aspects of the response to radiation. Alloying with Al2O3 further modulates the bandgap of Ga2O3 and defect behavior, offering potentially tunable radiation tolerance. These findings provide critical insights into the radiation response of Ga2O3 polymorphs, with implications for their use in aerospace and radiation-hardened power electronics. Future research should focus on direct comparisons of polymorphs under identical irradiation conditions, defect identification, and annealing strategies to enhance radiation tolerance. 

Minority carrier diffusion length in undoped p-type gallium oxide was measured at various temperatures as a function of electron beam charge injection by electron beam-induced current technique in situ using a scanning electron microscope. The results demonstrate that charge injection into p-type β-gallium oxide leads to a significant linear increase in minority carrier diffusion length followed by its saturation. The effect was ascribed to trapping of non-equilibrium electrons (generated by a primary electron beam) on metastable native defect levels in the material, which in turn blocks recombination through these levels. While previous studies of the same material were focused on probing a non-equilibrium carrier recombination by purely optical means (cathodoluminescence), in this work, the impact of charge injection on minority carrier diffusion was investigated. The activation energy of ∼0.072 eV, obtained for the phenomenon of interest, is consistent with the involvement of Ga vacancy-related defects. 

It has recently been demonstrated that electron beam injection into p-type β-gallium oxide leads to a significant linear increase in minority carrier diffusion length with injection duration, followed by its saturation. The effect was ascribed to trapping of non-equilibrium electrons (generated by a primary electron beam) at meta-stable native defect levels in the material, which in turn blocks recombination through these levels. In this work, in contrast to previous studies, the effect of electron injection in p-type Ga2O3 was investigated using cathodoluminescence technique in situ in scanning electron microscope, thus providing insight into minority carrier lifetime behavior under electron beam irradiation. The activation energy of ∼0.3 eV, obtained for the phenomenon of interest, is consistent with the involvement of Ga vacancy-related defects.