β-Ga2O3 is an ultra-wide bandgap semiconductor
with applications in power electronic devices. Revealing the transport characteristics of
β-Ga2O3 devices at various temperatures is
important for ...improving device performance and reliability. In this study, we fabricated a
Pt/β-Ga2O3 Schottky barrier diode with good
performance characteristics, such as a low ON-resistance, high forward current, and a
large rectification ratio. Its temperature-dependent current–voltage and
capacitance–voltage characteristics were measured at various temperatures. The
characteristic diode parameters were derived using thermionic emission theory. The
ideality factor n was found to decrease from 2.57 to 1.16 while the
zero-bias barrier height Φb0 increased from 0.47 V to 1.00 V when the
temperature was increased from 125 K to 350 K. This was explained by the Gaussian
distribution of barrier height inhomogeneity. The mean barrier height
Φ
¯
b0 = 1.27 V and zero-bias standard deviation
σ0 = 0.13 V were obtained. A modified Richardson plot gave a
Richardson constant A* of 36.02
A·cm−2·K−2, which is close to the theoretical value of 41.11
A·cm−2·K−2. The differences between the barrier heights determined
using the capacitance–voltage and current–voltage curves were also in line with the
Gaussian distribution of barrier height inhomogeneity.
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•The average formation energy of twin-B in β-Ga2O3 is 6.67 mJ·m−2.•The (100)-B plane of β-Ga2O3 follows the smooth interface growth mode.•Significant supercooling is the primary ...driving force for the forming of twins.•The nucleus kinetics of twins in β-Ga2O3 is described for the first time.
The twin boundary (TB) is a planar defect that both destroys the integrity of the crystal and significantly deteriorates the performance of semiconductor devices. However, limited research exists on the initial crystal nucleus kinetics of TB, which is a crucial aspect for a comprehensively understanding the twinning mechanism. Here, the nucleation kinetics process of TB has been thoroughly studied regarding crystal morphology, growth interface at the atomic scale, and first-principle calculations in β-Ga2O3. The nucleation kinetics process of TB originates from the smooth interface growth mode of (100)-B, which requires a significant degree of supercooling. During the crystal growth, the large degree of supercooling in front of the (100)-B plane at the three-phase boundary (TPB) leads to nucleation of TB. The twin type of β-Ga2O3 is recognized as twin-B among the two thermodynamically equivalent structures. It is a glide reflection twin whose glide process initiates with a 1/4 length of the 001 vector and then with a 1/2 length of the 010 vector. This study has developed the nucleation kinetics of TB, thus enriching the theory of crystal defects. The revealed relationship between TB and the smooth interface growth mode holds great significance for guiding the suppression of twins.
Tb3Sc1.95Lu0.05Al3O12 (TSLAG) magneto-optical crystal, with higher Verdet constant and lower absorption coefficient, is a potential candidate to substitute the commercial TGG crystals. In this work, ...bulk TSLAG crystals with maximum dimensions of Ø 35 × 60 mm3 have been successfully grown by the Czochralski (Cz) method with a 60 mm diameter crucible. The effective segregation coefficient of Tb3+, Sc3+, Lu3+, Al3+ ions were 0.99, 0.87, 0.99 and 1.09, respectively. The use of pure starting materials and lower thermal gradients during growth led to significantly improved crystal properties such as the optical transmission characteristics at 1064 nm. Also the thermal properties have been investigated in detail, providing primary reference data for applications in the field of intense lasers.
•Large size TSLAG single crystals were grown for magneto-optical applications.•Crystal quality was effectively improved using a low temperature gradient.•As-grown crystals perform excellent thermal and optical properties.
The sesquioxide Lu2O3 single crystal has enormous potential applications as host material for solid-state lasers operating at high average powers, and its development is limited by the lack of large ...sized single crystals with high quality. Compared with the traditional Czochralski (Cz) method, the edge-defined film-fed growth (EFG) method, employing a die or a shaper, doesn't make the grown crystal come into contact with the melt in crucible directly during the growth process. Therefore, the growth interface is stable and the serious bottleneck problems of a “w”-shaped isotherm in the Czochralski method could be avoided effectively. Herein, the EFG method may be a promising technique to obtain ultra-high temperature sesquioxide single crystals with a large size, and more importantly, high quality. Accordingly, the sesquioxide Lu2O3 single crystal has been grown controllably with an oriented seed by the EFG method for the first time and the EFG method is promoted to an extremely high temperature of 2450 °C. The dimensions of the grown crystal are Φ 25 × 30 mm3, and the difficulties encountered during the crystal growth have been discussed in detail. Furthermore, the quality of the crystal has been evaluated. The optical properties of the grown crystal have been investigated.
A Schottky barrier rectifier was fabricated with a (100)-oriented <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 substrate grown by the edge-defined film-fed ...method. The Sn-doped <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 substrate had an effective donor concentration of approximately <inline-formula> <tex-math notation="LaTeX">2\times 10^{17} </tex-math></inline-formula> cm −3 . High performance parameters were obtained, such as a high forward current (421 A/cm 2 at 2 V), low ON-resistance (2.9 <inline-formula> <tex-math notation="LaTeX">\text{m}\Omega \cdot </tex-math></inline-formula>cm 2 ), and short reverse recovery time (20 ns). Furthermore, the dynamic behavior of the device is characterized through test on the half-wave rectification of ac voltages at different frequency. The diode worked well at 100 kHz. At the end of the letter, we discuss how Ga 2 O 3 Schottky rectifier can operate at high frequency.
We fabricated β-Ga 2 O 3 photodetectors on bulk substrate and sapphire. Bulk Ga 2 O 3 photodetector demonstrates the improved responsivity compared with the device on sapphire, due to the higher ...crystal quality in bulk material. Optical gain is achieved in both the devices. For the first time, we report that the Ga 2 O 3 photodetector epitaxially grown on sapphire achieves a blueshift of bandgap in comparison with bulk device. Based on the measured responsivity characteristics, the direct and indirect E G of bulk Ga 2 O 3 are 4.78 and 4.59 eV, respectively. The Ga 2 O 3 photodetector on sapphire exhibits a maximum cutoff wavelength at 253 nm, corresponding to the direct E G of 4.90 eV. The increment of E G in Ga 2 O 3 on sapphire over bulk material is attributed to the residual strain in the film. The time-dependent photoresponse of the devices suggests that Ga 2 O 3 on sapphire might have more oxygen vacancies than the bulk material.
In this letter, MOS capacitors with bilayer dielectrics consisted of large bandgap Al2O3 and high-k HfO2 in different stacking order on n-type doped (100) β-Ga2O3 are investigated through C − V and J ...− V measurement. The C − V measurement results reveal that incoming HfO2 makes both bilayer structures attain an increasing dielectric constant, which means a better gate control ability in transistors comparing with single Al2O3. Additionally, the interface state density extracted by high-low frequency capacitance method suggests that Al2O3/(100)β-Ga2O3 with no treatment shows a comparative Dit value (8.0 × 1012 cm-2eV-1 to 2.2 × 1011 cm-2eV-1) with HfO2/(100)β-Ga2O3 (8.4 × 1012 cm-2eV-1 to 1.0 × 1011 cm-2eV-1) in energy range of 0.2 to 0.9 eV. Furthermore, HfO2/Al2O3/Ga2O3 showing a bigger forward breakdown voltage of 11.0 V than 7.8 V of Al2O3/HfO2/Ga2O3 demonstrates that inserted larger bandgap Al2O3 insulator between Ga2O3 semiconductor and high-k HfO2 dielectric can prevent gate leakage current more effectively. Accordingly, the HfO2/Al2O3/Ga2O3 can enhance gate control ability with an acceptable gate breakdown voltage and become an alternative choice in the design of the gate structure for Ga2O3 MOSFETs.
Owing to the advantages of ultra-wide bandgap and rich material systems, gallium oxide (Ga2O3) has emerged as a highly viable semiconductor material for new researches. This article mainly focuses on ...the growth processes, material characteristics, and applications of Ga2O3. Compared with single crystals and the epitaxial growth of other wide-bandgap semiconductors, large-size and high-quality β-Ga2O3 single crystals can be efficiently grown with a low cost, making them highly competitive. Thanks to the availability of high-quality single crystals, epitaxial films, and rich material systems, high-performance semiconductor devices based on Ga2O3 go through a booming development in recent years. The defects and interfaces of Ga2O3 are comprehensively analyzed owing to their significant influence on practical applications. In this study, the two most common applications of Ga2O3 materials are introduced. The high breakdown electric field, high working temperature, and excellent Baliga's figure-of-merit of Ga2O3 represent an inspiring prospect for power electronic devices. In addition, the excellent absorption in deep-ultraviolet band provides new ideas for optoelectronic detectors and ensures the dramatic progress. Finally, the summary, challenges, and prospects of the Ga2O3 materials and devices are presented and discussed.
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Fabricating a heterojunction photodetector is efficient to take advantage of the built‐in electric field formed by heterojunction and thus improve the performance of photodetector. Herein, a ...CuZnS/Ga2O3 type‐II heterojunction photodetector is designed and constructed by chemical bath deposition for the first time. The photodetector exhibits super high rectifying characteristics (5.7 × 104 at ± 1 V), high responsivity (48.01 mA W−1 at 0 V), and detectivity (1.83 × 1012 Jones at 0 V), which are higher than most of the reported inorganic devices as far as the authors know. Benefiting from built‐in electric field constructed by the CuZnS/Ga2O3 type‐II heterojunction, the photo‐induced electron and hole pairs are quickly separated by the built‐in electric field between the Ga2O3 and the CuZnS interface. Therefore, the photodetector constructed by CuZnS/Ga2O3 type‐II heterojunction shows a prominent self‐powered performance. At zero bias, the photodetector shows a fast photoresponse (rise time τr = 70 ms, decay time τd = 10 ms). These data of performance are significantly excellent to most of the reported Ga2O3 heterojunction photodetectors. These performances strongly suggest that the CuZnS/Ga2O3 photodetector has great potential in ultra‐high performance self‐powered solar‐blind photodetector.
A CuZnS/Ga2O3 type‐II heterojunction photodetector is constructed by sequential chemical bath deposition. Benefiting from built‐in electric field constructed by the CuZnS/Ga2O3 type‐II heterojunction, the photodetector exhibits super high rectifying characteristics (5.7 × 104 at ±1 V), high responsivity (48.01 mA W−1 at 0 V), and detectivity (1.83 × 1012 Jones at 0 V).
A new melilite single crystal CaYAl3O7 with dimensions of Φ26 × 60 mm3 has been grown successfully by the Czochralski method, taking into consideration as a potential high-temperature piezoelectric ...crystal for the first time. The rocking curve measurements indicate that the as-obtained CaYAl3O7 crystal is of high quality with a full width at half-maximum (FWHM) of 42.1 arcsec from the (001) reflection. The complete set of room temperature dielectric, elastic, and piezoelectric constants of CYAM crystal were determined using resonance techniques and impedance analysis. Our results show the piezoelectric strain constants d14 and d36 are 12.6 and 2.18 pC/N, respectively, with the corresponding electromechanical coupling coefficients of k14 = 18.06% and k36 = 5.45%, indicating the crystal is a promising candidate for piezoelectric applications. The structural polyhedron distortions dipole moments of CYAM crystal were analyzed in detail, and the relationship between the crystal structure and the piezoelectric properties has also been discussed.
•High quality CaYAl3O7 crystal was grown by Czochralski method.•The electro-elastic properties of CaYAl3O7 crystal were determined.•The dipole moments of CaYAl3O7 crystal were calculated and analyzed.•CaYAl3O7 crystal is promising for high temperature piezoelectric applications.
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