Structure Of β-Ga2O3 Research Articles

High-temporal Dynamic Self-powered β-Ga2O3/GaN Heterojunction Ultraviolet Photodetector

Abstract In this report, we successfully fabricate a high-temporal-response β-Ga2O3/GaN heterojunction ultraviolet photodetector. A high-quality 2-inch single-crystalline β-Ga2O3 film is grown on GaN template with a GaOx buffer layer using Plasma-Assisted Molecule Beam Epitaxy (PA-MBE). Based on the as-grown film, a self-powered heterojunction detector with a unilateral recessed interdigital electrode is constructed. The device exhibits a broad-spectrum ultraviolet selective response characteristics with a cut-off edge at 330 nm and achieves a responsivity of 0.7 A/W under zero bias. Under a bias of 5 V, the rapid photoresponse rise time and decay time are 30 μs and 10.8 ms, respectively, and the photo-to-dark current ratio (PDCR) reaches 103. Considering the heterojunction energy band structure of β-Ga2O3/GaN, the work function difference of 0.43 eV facilitates electron migration and enables the self-powered operation. These results demonstrate a promising and efficient approach for developing high-performance, self-powered UV photodetectors and offer a robust alternative to conventional high-energy-consuming UV detection systems.

Plane Selective Metal-Assisted Chemical Etching for Good Ohmic Contact to β-Ga2O3

With the advent of the first silicon-based transistor in 1954, integrated circuit technology has advanced substantially. Nonetheless, the progression of high-power devices has been hindered by the inherent limitations of silicon's narrow bandgap (1.1 eV) and its relatively low breakdown voltage (~0.3 MV/cm), necessitating the exploration of alternative high-power semiconductor materials. Leading candidates for next-generation high-power semiconductors include wide bandgap materials such as gallium nitride (GaN) and silicon carbide (SiC), as well as ultra-wide bandgap materials like gallium oxide (Ga2O3, with a bandgap of 4.8-5.3 eV and breakdown field of ~10 MV/cm). Ga2O3 is known for its five different phases (α, β, γ, κ, ε) and exhibits high thermal, chemical, and radiation hardness, along with physical stability, making it suitable for high-power semiconductor devices in extreme and aerospace environments. Among five phases, the β-Ga2O3 is garnering significant research interest for its stability, monoclinic structure, and the capability of being grown over large areas with high crystallinity via melt growth methods. The physical and chemical stability of Ga2O3 has rendered conventional etching techniques ineffective, prompting the exploration of alternative methods such as inductively coupled plasma reactive ion etching (ICP-RIE) and metal-assisted chemical (MAC) etching. In contrast to ICP-RIE, which may induce defects via ion bombardment in the dry etching process, MAC etching passivates defects through wet etching process. The characteristics of MAC etching enable selective etching of β-Ga2O3 planes through patterning of the metal catalyst which locally amplifies the etching reactions. The highly asymmetric monoclinic crystal structure (C2/m) of β-Ga2O3 contributes to the anisotropic electrical properties observed in β-Ga2O3. Forming Ohmic contacts with low on resistance is crucial in many electronic devices, and research has been conducted to identify crystal orientations that demonstrate low contact resistance. Previous studies focused on the comparison of contact resistances in surface contacts on substrates with different surface orientations. Comparing across distinct substrates failed to account for the variations in contact resistance caused by doping and defects. In this study, MAC etching was performed to form trench contacts on an undoped β-Ga2O3 (Nd-Na ~1017) bulk substrate with a (010) plane as the surface orientation. The trenches had orientations of (001), (100), (101), (102), (201), and (-201) planes, and TLM patterns with channel lengths of 5, 10, 15, 20, 25, and 30 μm were fabricated for each plane. This approach eliminated the effects of doping and defects, allowing for the precise examination of contact resistance in each plane orientations. Analyzing the contact resistance of β-Ga2O3 based on plane orientations will contribute to understanding the anisotropic electrical properties of β-Ga2O3 and advance the industrialization of β-Ga2O3 in the field of high-power electronic devices. Figure 1

Physical and enhanced photocatalytic MO dye degradation behaviour of Zn doped β-Ga2O3 microrods

This work explored the effects of Zn doping on the structural, micrographic, optical and photocatalytic behaviour of gallium oxide (β-Ga2O3) microrods. The X-ray diffractogram (XRD) and Raman spectral analyses confirmed the monoclinic structure of β-Ga2O3, with a shift to lower angles in the XRD pattern indicating Zn incorporation into the Ga2O3 lattice. The Scanning electron microscopy (SEM) images revealed a rod-like shape, with the diameter decreasing from 604 nm to 573 nm with Zn doping. Further analysis using TEM, HR-TEM, SAED, EDX, and elemental mapping confirmed the shape, crystallinity, crystal structure, and elemental distribution. The interplanar spacings were measured as 0.4 and 0.2 nm, corresponding to the (002) and (−311) planes of β-Ga2O3. UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) showed a slight shift in the absorption edge, while photoluminescence (PL) analysis demonstrated strong UV and weak visible light emission. Photocatalytic results revealed a high efficiency of dye degradation,(i.e) 98 % (20 ppm) and 89 % (30 ppm) against methyl orange (MO) dye aqueous solution over 150 min, with a rate constant of 0.02/min and 0.01/min, respectively for 1.5 wt% Zn doping. This suggests that the Zn-doped material holds promise as a photocatalyst for wastewater treatment applications.

Enhanced hypersensitive (5D0→7F2) transition characteristics of Eu3+ doped β-Ga2O3 microrods

Exploring and realizing the luminescence characteristics of rare earth metal (RE) ions doped gallium oxide (Ga2O3) is crucial for developing optoelectronic device applications. The current research used the solid-state reaction approach to synthesize Ga2O3 microrods doped with various europium (Eu3+) concentrations (0.1, 0.2, 0.3, 0.5, 0.75, and 1 mol). X-ray diffraction (XRD) and Raman spectral analyses confirm the monoclinic structure of β-Ga2O3. The intensity of the Raman phonon modes decreased and a peak shift was observed for Eu:β-Ga2O3. The electron microscopy (SEM, TEM) images depicted a nearly uniform distribution of microrods for undoped and Eu:β-Ga2O3 samples. The interplanar distance (d = 0.290 nm, 0.561 nm, and 0.433 nm), from HR-TEM images, corresponding to (0 0 4), (1 0 0), and (1 0 2) crystallographic orientations confirm the monoclinic structure of β-Ga2O3. The elemental mapping images showed a nearly homogeneous Ga, O, and Eu distribution. The UV–visible diffuse reflectance spectroscopy (UV-DRS) showed a notable reduction in the bandgap as the Eu3+ concentration increased. The emission spectra of Eu: β-Ga2O3 microrods showed a narrow red emission at 612 nm (5D0 → 7F2), which relates to the 5D0 → 7Fj (j = 0, 1, 2, 3) energy level arising from an intra-4f transition of Eu3+ ions upon 394 and 465 nm excitation. The red emission was found to increase with Eu content up to 0.5 mol.%. A quenching of emission due to the multipole–multipole interactions was obtained beyond 0.5 mol.% of Eu. The absolute quantum yield (η) calculated for Eu: β-Ga2O3 (0.5 mol.%) was 3.82 %. The luminescence decay curve using the bi-exponential fit and the average lifetime (τ) of the Eu: β-Ga2O3 (0.5 mol.%) was found to be ∼0.172 ms. CIE chromaticity and correlated color temperature analyses of Eu:β-Ga2O3 microrods yielded a red emission with a superior color purity (93 %). The obtained results suggest that Eu:β-Ga2O3 (0.5 wt.%) microrods could be one of the potential candidates for red light sources.

Oxygen-close-packed (310)-plane substrates of β-Ga2O3 grown by the casting method

The highly anisotropic crystal structure of β-Ga2O3 gives rise to a variety of crystal planes, among which the (310) plane is a potentially stable close-packed plane for the O sublattice. In this paper, we report the β-Ga2O3 single crystal and substrates with a (310) major plane grown by the spontaneous nucleation technique in the casting method. High-quality crystal growth and substrate processing were confirmed by the 25.67 arc sec full width at half maximum and the 0.25 nm surface roughness. The nanoindentation experiments revealed the (310) substrate's better elastic recovery than that of (100) substrate. The Young's modulus and hardness of (310) substrates were 200 and 7.6 GPa, respectively. The surface barrier height and the Schottky barrier height were 1.25 and 0.92 eV, respectively. First principles calculations identified the (310)-Ga-I plane as the most stable surface configuration of the (310) plane under oxygen-poor condition, with a surface energy density of 1.48 J/m2. The (310) twin boundary formation around the O sublattice has a high energy density of 0.55 J/m2, suggesting its unlikelihood of spontaneous formation. These properties of (310) plane facilitate a high-quality crystal processing and epitaxial growth, thus endowing potential applications in high-quality power devices. Furthermore, the growth and fabrication of the (310) plane provide a route toward understanding the properties of β-Ga2O3 and advancing the growth techniques of oxide crystals.

First-principle calculations of the electronic structure and optical properties of β-Ga2O3 with various vacancy defects

In this work, the effects of five types of vacancy defects on the electronic, optical and thermodynamic properties of β-Ga2O3 were investigated using first-principle calculations. The findings revealed that oxygen vacancies were more prevalent than gallium vacancies, with tetrahedral gallium vacancies being easier to form than octahedral ones. Vacancy defects induced a shift in the energy bands towards the lower energy end, with gallium vacancies reducing the bandgap from 4.9 eV to 3.1 eV, while the effect of oxygen vacancies on the bandgap was negligible. Oxygen vacancies introduced deep impurity levels near the Fermi level, while gallium vacancies introduced shallow impurity levels, primarily due to contributions from O-2p, Ga-4s, and Ga-4p orbital electrons. The differential charge density diagrams illustrated that gallium vacancies had a more pronounced impact on electronic distribution compared to oxygen vacancies, with VO3 exhibiting the least influence. As the temperature increases, the β-Ga2O3 with VO1 and VO2 exhibit higher thermodynamic stability compared to the intrinsic β-Ga2O3 and the one with VO3, while the intrinsic β-Ga2O3 has a superior heat capacity value compared to the β-Ga2O3 containing the five vacancy defects. The defect energy levels resulting from vacancies enhanced light absorption and conductivity, particularly oxygen vacancies, which improved the absorption capacity of β-Ga2O3 in the visible light range. These findings provide valuable insights for elucidating optical absorption experimental phenomena and photoluminescence.

Deep Ultraviolet Optical Anisotropy of β-Gallium Oxide Thin Films.

β-Crystalline phase gallium oxide (β-Ga2O3) is an ultrawide bandgap material with prospective applications in electronics and deep ultraviolet (DUV) optoelectronics and optics. The monoclinic crystal structure of β-Ga2O3 results in optical anisotropy to incident light with different polarization states. This attribute can lead to different optical applications in the DUV. In this article, we investigated the optical properties of β-Ga2O3 thin films grown by pulsed laser deposition technique on sapphire substrates with different crystallographic orientations. Marked in-plane polarization anisotropy, determined by reflectance and Raman spectroscopy, was observed for β-Ga2O3 films deposited on an r-cut sapphire substrate. In contrast, isotropic optical properties were observed in β-Ga2O3 films deposited on a c-cut sapphire substrate.

Band alignment and electronic structure of β-Ga2O3 (−201) grown on Si- and C-faces of 4H–SiC substrates

In this manuscript, epitaxial beta-Ga2O3 films were prepared on 4H–SiC substrates via low-pressure chemical vapor deposition. β-Ga2O3 thin films with a (−201) preferred orientation were formed on (Si-face) 4H–SiC (0001) and (C-face) 4H–SiC (000‾1) with surface roughness values of 2.92 and 3.97 nm, respectively. The band alignments of both Si- and C-faces of β-Ga2O3/4H–SiC heterojunctions were investigated via X-ray photoelectron spectroscopy. The bandgaps for Si- and C-faces of β-Ga2O3 were measured to be 4.92eV and 4.79eV, respectively. The band diagrams revealed that the Si- and C-faces of β-Ga2O3/4H–SiC heterojunctions are straddling-gap (type I). The valence band offsets were determined to be 1.46 ± 0.05 and 1.19 ± 0.05 eV for Si- and C-faces, respectively. The conduction band offsets were shown to be 0.20 ± 0.05 eV for the Si-face and 0.34 ± 0.05 eV for the C-face. The comprehensively evaluation of the band offsets for Si- and C-faces of β-Ga2O3/4H–SiC heterojunctions have significant meaning for the design and optimization of electronic devices.

Characteristics of 4-inch (100) oriented Mg-doped β-Ga2O3 bulk single crystals grown by a casting method

In this Letter, 4-inch diameter (100) magnesium-doped monoclinic gallium oxide (Mg:β-Ga2O3) bulk single crystals were grown by a casting method. The crystallographic structure, electrical, optical properties, and defects of Mg-doped β-Ga2O3 was thoroughly investigated by XRD rocking curves, AFM, non-contact resistivity measurements, XPS, optical transmission spectra, Raman spectroscopy, and defect-selective chemical etching processes. Comparing to the UID samples, the larger bandgap of 4.75 eV and high resistivity of 3.50×1012 Ω∙cm indicated Mg a proper dopant for fabricating semi-insulating β-Ga2O3 substrates which could be preferred for power devices. XPS spectra exhibited the ability of Mg2+ to inhibit the formation of oxygen vacancy defects in the crystals. Meanwhile, the high crystalline quality and low density of defects demonstrated the advantages of casting method in achieving large-size and high-quality β-Ga2O3 bulk single crystals with changeable resistivity. This result indicates a high potential to achieve high-quality and low-cost substrates which satisfy the requirement of high-performance power electronic devices.

Fabrication, properties, and photodetector of β-(AlxGa1-x)2O3/GaN heteroepitaxial films grown by MOCVD

In this paper, β-(AlxGa1-x)2O3 heteroepitaxial films with different Al content were successfully prepared on p-GaN substrates by MOCVD method. When the “x” values are in a range of 0–0.38, the (AlxGa1-x)2O3 grown on p-GaN is an epitaxial film, maintaining the lattice structure of β-Ga2O3, and presenting an adjustable bandgap of 5.0–5.93 eV. When x = 0.45, the film is amorphous, and present a low bandgap of ∼5.73 eV due to the band tail formed by a large number of defects. φ scanning, HRTEM and SAED results showed that the prepared film was a six-fold domain structure and had an epitaxial relationship with the substrate of β-(AlxGa1-x)2O3 (2‾01) || GaN (0001) with β-(AlxGa1-x)2O3 [102] || GaN <1-100>. The photodetector (PD) based on β-(AlxGa1-x)2O3/GaN p-n junction presents high photoresponsivity (0.045 A/W) at 218 nm. The wavelength is far lower than the optimal responsive wavelength (254 nm) of β-Ga2O3 in previous reports, meaning that β-(AlxGa1-x)2O3 can be used to fabricate shorter wavelength UV photodetector.

Thermalization of radiation-induced electrons in wide-bandgap materials: A first-principles approach

The present study is concerned with simulating the thermalization of high-energy charge carriers (electrons and/or electron–hole pairs), generated by ionizing radiation, in diamond and β-Ga2O3. Computational tools developed by the nuclear/particle physics and electronic device communities allow for accurate simulation of charge-carrier transport and thermalization in the high-energy (exceeding ∼100 eV) and low-energy (below ∼10 eV) regimes, respectively. Between these energy regimes, there is an intermediate energy range of about 10–100 eV, which we call the “10–100 eV gap,” in which the energy-loss processes are historically not well studied or understood. To close this “gap,” we use a first-principles approach (density functional theory) to calculate the band structure of diamond and β-Ga2O3 up to ∼100 eV along with the phonon dispersion, carrier-phonon matrix elements, and dynamic dielectric function. Additionally, using the first-order perturbation theory (Fermi's golden rule/first Born approximation), we calculate the carrier-phonon scattering rates and the carrier energy-loss rates (impact ionization and plasmon scattering). With these data, we simulate the thermalization of 100-eV electrons and the generated electron–hole pairs by solving the semiclassical Boltzmann transport equation using Monte Carlo techniques. We find that electron thermalization is complete within ∼0.4 and ∼1.0 ps for diamond and β-Ga2O3, respectively, while holes thermalize within ∼0.5 ps for both. We also calculate electron–hole pair creation energies of 12.87 and 11.24 eV, respectively.

Influence of external electric field on electronic structure and optical properties of β-Ga2O3: a DFT study.

The influence of different electric fields on the electronic structure and optical properties of β-Ga2O3 was studied by GGA+U method. The results show that appropriate electric field intensity can regulate the band gap of β-Ga2O3 more effectively to improve the photoelectric characteristics. The band gap value of intrinsic β-Ga2O3 is 4.865 eV, and decreases from 4.732 to 2.757 eV with the increase of electric field intensity from 0.05 to 0.20 eV Å-1. The length of the O-Ga bond along the electric field increases the fastest with the electric field intensity, and the distance between O and Ga reaches 2.52 Å when the electric field intensity is 0.20 eV Å-1. A new peak appears in the real and imaginary parts of the dielectric function for β-Ga2O3 in the low frequency region under the electric field, and the conductivity increases obviously. The optical absorption peaks induced by the electric field were observed in the wavelength range of 400-600 nm. The optical absorption of β-Ga2O3 is enhanced with an increase of electric field intensity, exhibiting a maximum value with the electric field of 0.15 eV Å-1. The electric field above 0.15 eV Å-1 causes a decrease of optical absorption intensity.

Electron–phonon effects and temperature-dependence of the electronic structure of monoclinic β-Ga2O3

Gallium oxide (Ga2O3) is a promising semiconductor for next-generation high-power electronics due to its ultra-wide bandgap and high critical breakdown field. To utilize its unique electrical properties for real-world applications, an accurate description of its electronic structure under device-operating conditions is required. Although the majority of first-principles models focus on the ground state, temperature effects govern the key properties of all semiconductors, including carrier mobility, band edge positions, and optical absorption in indirect gap materials. We report on the temperature-dependent electronic band structure of β-Ga2O3 in a wide temperature range from T = 0 to 900 K using first-principles simulations and optical measurements. Band edge shifts from lattice thermal expansion and phonon-induced lattice vibrations known as electron–phonon renormalization are evaluated by utilizing the quasi-harmonic approximation and the recently developed “one-shot” frozen phonon method, respectively. Electron–phonon effects and thermal expansion together induce a substantial temperature-dependence on the bandgap, reducing it by more than 0.5 eV between T = 0 and 900 K, larger than that observed in other wide bandgap materials. Key implications, including an increase in carrier concentrations, a reduction in carrier mobilities due to localization of band edge states, and an ∼20% reduction in the critical breakdown field, are discussed. Our prediction of temperature-dependent bandgap matches very well with experimental measurements and highlights the importance of accounting for such effects in first-principles simulations of wide bandgap semiconductors.

Effect of RF power and gas ratio on the sidewall of β-Ga2O3 films via inductively coupled plasma etching

The beveled mesa structure of β-Ga2O3 has attracted wide attention because it can significantly weaken the peak electric field and increase the breakdown voltage. In this study, β-Ga2O3 beveled mesa has been modulated via inductively coupled plasma (ICP) etching with the etching precursors of BCl3 and Ar. And the morphology of the sidewall has been investigated by properly adjusting the etching parameters, realizing different beveled angles owing to the different ratios of chemical etching and physical etching. The effect of ICP etching on the sidewall morphology of the β-Ga2O3 beveled mesa was also studied. This study provides important guidance for the realization of higher-power devices based on β-Ga2O3.

Atomic-scale characterization of structural damage and recovery in Sn ion-implanted β-Ga2O3

β-Ga2O3 is an emerging ultra-wide bandgap semiconductor, holding a tremendous potential for power-switching devices for next-generation high power electronics. The performance of such devices strongly relies on the precise control of electrical properties of β-Ga2O3, which can be achieved by implantation of dopant ions. However, a detailed understanding of the impact of ion implantation on the structure of β-Ga2O3 remains elusive. Here, using aberration-corrected scanning transmission electron microscopy, we investigate the nature of structural damage in ion-implanted β-Ga2O3 and its recovery upon heat treatment with the atomic-scale spatial resolution. We reveal that upon Sn ion implantation, Ga2O3 films undergo a phase transformation from the monoclinic β-phase to the defective cubic spinel γ-phase, which contains high-density antiphase boundaries. Using the planar defect models proposed for the γ-Al2O3, which has the same space group as β-Ga2O3, and atomic-resolution microscopy images, we identify that the observed antiphase boundaries are the {100}1/4 ⟨110⟩ type in cubic structure. We show that post-implantation annealing at 1100 °C under the N2 atmosphere effectively recovers the β-phase; however, nano-sized voids retained within the β-phase structure and a γ-phase surface layer are identified as remanent damage. Our results offer an atomic-scale insight into the structural evolution of β-Ga2O3 under ion implantation and high-temperature annealing, which is key to the optimization of semiconductor processing conditions for relevant device design and the theoretical understanding of defect formation and phase stability.

First-principles study of the influence of Nb doping on the electronic structure and optoelectronic properties of β-Ga2O3

The electronic structure and optoelectronic properties of Nb-doped β-Ga2O3 were investigated by using plane wave ultrasoft pseudopotential generalized gradient approximation +U (GGA + U) method based on density functional theory. Four supercell models, namely, Ga23O36Nb1, Ga32O48, Ga39O60Nb1, and Ga47O72Nb1, were constructed. Results show that the formation energy of the doped system is lower and has higher stability under Ga-rich conditions than in O-rich conditions. With the increment in Nb doping concentration, the formation energy and lattice constant gradually increase, the stability of the system gradually decreases, and the band gap of the system gradually narrows. As the doping concentration increase, the absorption intensity increases. Furthermore, the increasing doping concentration accelerates the separation of holes and electrons, prolongs the carrier lifetime, and enhances conductivity. These conclusions provide a certain theoretical basis for the wide application of β-Ga2O3.

Band offset and electrical properties of ErZO/β-Ga2O3 and GZO/β-Ga2O3 heterojunctions

The fabrication of ohmic contacts on wide bandgap semiconductors, such as β-Ga2O3, is difficult as the scarcity of metals with low-enough work function. The insertion of n+-doped metal oxide layer between metal and the β-Ga2O3 layers are effective for improving the ohmic behaviour. β-Ga2O3, Erbium doped ZnO (ErZO), and Gallium doped ZnO (GZO) films with high crystallinity were deposited by pulsed laser deposition. The band offsets and electrical properties of ErZO/β-Ga2O3 and GZO/β-Ga2O3 heterojunctions were investigated, which revealed the nested gap (type I) structures. The conduction band offsets were determined to be 0.88 eV for ErZO and 0.96 eV for GZO, and their corresponding valance band offsets were found to be 0.46 eV and 0.16 eV. In addition, the difference of the work functions between ErZO and β-Ga2O3 was 0.05 eV; and 0.16 eV between GZO and β-Ga2O3. Solar blind UV detector having fork electrode structure of as-grown β-Ga2O3/ErZO/Ti/Au structure showed good ohmic performance and have superior detector performance comparing with the other two electrode structures, which was ascribed to ErZO’s low band offset and small work function difference with β-Ga2O3. The present result provides an option for fabricating ohmic contact on β-Ga2O3 without the need for post-growth annealing.

Atomic-scale characterization of structural and electronic properties of Hf doped β-Ga2O3

In this Letter, we investigate the atomic and electronic structure of a Hf-doped beta-gallium oxide (β-Ga2O3) single crystal using high resolution scanning transmission electron microscopy imaging and electron energy loss spectroscopy. Ultraviolet-visible (UV-Vis)-near-infrared absorption measurements and density functional theory calculations are performed to further connect the nanoscale observation to the macroscale properties arising from the atomic structure. The Hf-doped sample was grown from the melt with a nominal Hf concentration of 0.5 at. %. We show that the Hf dopants prefer to occupy octahedral over tetrahedral sites by 0.68 eV and have some resistance to form precipitates due to a repulsive interaction of 0.17 eV between Hf atoms on neighboring sites. Also, the presence of Hf atoms on either tetrahedral or octahedral sites do not significantly affect the crystal structure of β-Ga2O3. Finally, the bandgap values of the Hf doped β-Ga2O3 obtained by electron energy loss spectroscopy and UV-Vis-spectroscopy were Eg = 4.83 ± 0.1 and 4.75 ± 0.02 eV, respectively, similar to the values reported for unintentionally doped β-Ga2O3 crystals. All these results make Hf an excellent dopant candidate for β-Ga2O3.

Determination of type-ΙΙ band alignment β-Ga2O3/GaAs heterojunction interface by x-ray photoelectron spectroscopy

A high-quality β-Ga2O3 film was grown on a (111) GaAs substrate using the metal organic chemical vapor deposition method. The band alignment of the β-Ga2O3/GaAs heterojunction interface was determined by x-ray photoelectron spectroscopy. The energy-band structure of β-Ga2O3/GaAs was constructed based on the binding energies of Ga 3d and As 3d core levels as well as valence band maximum values. The valence band offset was determined to be 3.50 ± 0.05 eV. As a consequence, a type-ΙΙ heterojunction with a conduction band offset of 0.12 ± 0.05 eV was determined in the present study. The accurate determination of the band alignment of the β-Ga2O3/GaAs heterojunction provided useful information for the application in β-Ga2O3/GaAs-based devices.

Effect of transition metals doping on electronic structure and optical properties of β-Ga2O3

The effects of transition metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) doping on the stability, electronic structure and optical properties of β-Ga2O3 have been studied using GGA and GGA + U. The results show that the U value can correct the strong interaction of the d-layer, causing orbital hybridization and affecting the position and number of impurity energy levels. It can move the conduction band to higher energy levels and weaken the role of Ga-3p in the valence band. The Ti-doped β-Ga2O3 is easily formed, followed by V, Cr, Sc, Fe, Mn, Co, Ni, Cu, and Zn doping. Some bands change regularly with the increase of atomic number. All systems become degraded semiconductors after doping. All doping will make the β-Ga2O3 red shift. Among them, the absorption intensity of Cu doping in the visible light range is significantly improved.