The heteroepitaxial growth of (3-Ga2O3 on the commonly used sapphire substrate presents great challenges due to their large lattice mismatch. To address this, a NiO buffer layer is proposed to improve the quality of the heteroepitaxial (3-Ga2O3, as it has a lower lattice mismatch (0.46 %) with (3-Ga2O3 compared to sapphire (6.6 %). Traditional epitaxial growth methods for Ga2O3 are not compatible with NiO growth, so an inexpensive, nonvacuum, and convenient Mist-CVD technology is used for heterogeneous (3-Ga2O3 growth in this study. XRD and TEM results demonstrate the high quality of (3-Ga2O3 sample with the clear interface between materials. Introducing a NiO buffer layer enables the Full Width at Half Maximum (FWHM) and root-mean-square (RMS) roughness of (3-Ga2O3 to reduce from 0.726 degrees to 0.514 degrees and from 7.47 nm to 3.34 nm respectively. Additionally, through the UDM analysis model, micro-strain within the film is found to significantly decrease. This work proposes a novel approach to improve the quality of (3-Ga2O3 heteroepitaxial growth on sapphire substrate, contributing to the advancement of Ga2O3 materials and devices.

The heteroepitaxial growth of β-Ga2O3 on the commonly used sapphire substrate presents great challenges due to their large lattice mismatch. To address this, a NiO buffer layer is proposed to improve the quality of the heteroepitaxial β-Ga2O3, as it has a lower lattice mismatch (0.46 %) with β-Ga2O3 compared to sapphire (6.6 %). Traditional epitaxial growth methods for Ga2O3 are not compatible with NiO growth, so an inexpensive, non-vacuum, and convenient Mist-CVD technology is used for heterogeneous β-Ga2O3 growth in this study. XRD and TEM results demonstrate the high quality of β-Ga2O3 sample with the clear interface between materials. Introducing a NiO buffer layer enables the Full Width at Half Maximum (FWHM) and root-mean-square (RMS) roughness of β-Ga2O3 to reduce from 0.726° to 0.514° and from 7.47 nm to 3.34 nm respectively. Additionally, through the UDM analysis model, micro-strain within the film is found to significantly decrease. This work proposes a novel approach to improve the quality of β-Ga2O3 heteroepitaxial growth on sapphire substrate, contributing to the advancement of Ga2O3 materials and devices.

Due to the excellent responsivity and high rejection ratio, Ga2O3-based solar-blind ultraviolet photodetectors (PDs) are attracting more and more attention. The excellent material quality ensures great performance of PDs. In this review, we summarize recent advancements in growth methods of beta-Ga2O3 bulk and thin films. Based on high-quality substrates and thin films, numerous state-of-art Ga2O3-based PDs have been reported in decades. Therefore, we collect some representative achievements in Ga2O3-based PDs, summarizing the development process of each type of structure. Furthermore, the advantages and disadvantages of different structures are also discussed to provide practical reference for researchers in this field. Additionally, inspired by the excellent performance of Ga2O3-based PDs, many research teams have also explored the applications based on solar-blind detection. We summarize three application fields, including imaging, light communication, and optical tracing, introducing some excellent works from different teams. Finally, we evaluate the outlook and remaining challenges in the future development of Ga2O3-based PDs.

In this work, we demonstrated a high-performance NiO/ NiO/beta-Ga2O3 heterojunction photodetector using piranha solution pretreatment technology. After treatment, the NiO/NiO/beta-Ga2O3 heterojunction exhibited an excellent electrical performance, including a higher on/off ratio of 1 x 10(7), a lower reverse current of 0.28 pA, and an improved ideal factor. Additionally, the solar-blind detection performance of treated sample was significantly enhanced, including a 2900% increase in photo-to-dark-current ratio (PDCR), a 140% increase in responsivity, and a 900% increase in detectivity. Notably, excellent rise time and decay time were observed to be 60 and 50 ms after treatment, demonstrating an impressive reduction of 97% and 98%, respectively. This fast response characteristic has a wide range of applications. Thus, we conducted an optical communication test based on an original solar-blind communication system. Data transmission was successfully achieved ten times with a short sampling time of 100 ms. These results illustrate the effectiveness of piranha solution pretreatment in elevating the performance of Ga2O3-based heterojunction photodetector.

In this work, we report on achieving enhanced performance NiOx/beta gallium oxide (beta-Ga2O3) heterojunction p-n diodes (HJDs) through synergistic interface engineering (SIE), which can greatly improve the electrical characteristics and interface characteristics of HJDs. It is shown that the NiO $_{\textit{x}}$ surface undergoes morphological improvement and hole concentration enhancement after the UV/ozone treatment (UVO). Owing to the improved interfacial properties of Ni/NiOx , the forward conduction current of NiOx(beta-Ga2O3) HJD has significantly increased. Furthermore, the HJD performance can be improved by SIE with UVO and postannealing, especially for the reverse breakdown characteristics. Finally, a high-performance HJD without any terminal structure is obtained, which exhibits a low specific on-resistance of 2.47 m Omega.cm2 and a high breakdown voltage of 1355 V, yielding a high Baliga's figure of merit (BFOM) of 0.743 GW/cm2 , which is a 219.17% enhancement in performance compared to untreated device. This work offers a practical and effective strategy for developing advanced Ga $_{\text{2}}$ O $_{\text{3}}$ devices with exceptional performance metrics, paving the way for future technological breakthroughs.

Gallium oxide (Ga2O3) p–n heterojunctions play an important role in addressing the difficulties in Ga2O3 p-type doping. Therefore, an efficient and economical fabrication method needs to be established to create single-crystal Ga2O3 heterojunctions for device applications. In this work, we successfully achieved epitaxial growth of single-crystal nickel oxide (NiO) and β-Ga2O3 heterojunctions based on the low-cost and vacuum-free mist chemical-vapor deposition. The full width at half maximum of the X-ray diffraction rocking curves of NiO (111) and β-Ga2O3 (−201) reached 0.077° and 0.807°, respectively. The energy band between NiO and β-Ga2O3 has a Type II heterojunction. Finally, we prepared a quasi-vertical diode based on the NiO/β-Ga2O3 heterojunction, which exhibits obvious rectification characteristics of the p–n junction and provides a reverse breakdown voltage of 117 V. This work proposes a low-cost fabrication method for β-Ga2O3 p–n heterojunctions.

In this work, we report on achieving enhanced performance NiO $_{\textit{x}}$ /beta gallium oxide ( $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ ) heterojunction p-n diodes (HJDs) through synergistic interface engineering (SIE), which can greatly improve the electrical characteristics and interface characteristics of HJDs. It is shown that the NiO $_{\textit{x}}$ surface undergoes morphological improvement and hole concentration enhancement after the UV/ozone treatment (UVO). Owing to the improved interfacial properties of Ni/NiO $_{\textit{x}}$ , the forward conduction current of NiO $_{\textit{x}}$ / $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ HJD has significantly increased. Furthermore, the HJD performance can be improved by SIE with UVO and postannealing, especially for the reverse breakdown characteristics. Finally, a high-performance HJD without any terminal structure is obtained, which exhibits a low specific on-resistance of 2.47 m $\Omega \cdot$ cm $^{\text{2}}$ and a high breakdown voltage of 1355 V, yielding a high Baliga’s figure of merit (BFOM) of 0.743 GW/cm $^{\text{2}}$ , which is a 219.17% enhancement in performance compared to untreated device. This work offers a practical and effective strategy for developing advanced Ga $_{\text{2}}$ O $_{\text{3}}$ devices with exceptional performance metrics, paving the way for future technological breakthroughs.

Gallium Oxide (Ga2O3) holds significant potential for the next generation of electronic devices following SiC and GaN due to its ultra-wide bandgap of approximately 4.5 eV - 4.9 eV and high theoretical critical breakdown field strength of 8 MV/cm. Nonetheless, Ga2O3 has a naturally low thermal conductivity, resulting in limited device output performance and hindering Ga2O3 devices from reaching their full theoretical potential. In this study, we demonstrate that the appropriate thermal management strategy can solve the above challenges. By comparing the thermal control schemes including the Ga2O3 FET devices on the original substrate, the thinned Ga2O3 substrate, the high thermal conductivity substrate, the heat sink packaging, and the flip-chip packaging, it is demonstrated that the flip-chip model is the most effective strategy to improve the heat dissipation performance of the Ga2O3 device. By utilizing the appropriate carrier in flip-chip packaging, the temperature elevation of the device at 2 W/mm power density will be diminished by around 91% in contrast to the initial basic device. Furthermore, the output performance of the device demonstrates significant enhancement. This thermal management technique successfully resolves the severe heat dissipation issue prevalent in Ga2O3 devices and eliminates primary obstacles concerning the industrialization of Ga2O3 RF and power devices.