In this study, we investigated the influence of post-deposition annealing (PDA) process on lithium phosphate (Li3PO4) solid-state thin films on silicon carbide (SiC) substrate in terms of materials and electrical properties. Li3PO4 thin films were deposited through radio frequency (RF) sputtering and post-deposition annealing was performed in a temperature range of 200–400 °C. The Li3PO4 thin films show typical amorphous structures, and no changes are observed even after 400 °C PDA process. The Li 1 s/P 2p ratio varies with changing the annealing temperature and the highest Li is detected under 300 °C annealing, where the ionic conductivity increases to 1.00 × 10−4 S/mm at the same temperature. The rectification ratio of the 300 °C annealed device is obtained as 1.45 × 103, which is 23 times higher value than as-deposited Li3PO4/SiC device without annealing. This result suggests that the delicate control of Li3PO4 deposition could provide a significant enhancement on the electrical devices and the solid electrolyte batteries.
This study investigated the impact of ultraviolet/ozone (UV/O3) treatment on the electrical and morphological characteristics of Pt/Ga2O3 Schottky barrier diodes (SBDs). Current voltage characteristics were measured within the temperature range of 298-423 K. The fabricated Pt/Ga2O3 SBDs exhibit significant temperature-dependent variations of Schottky barrier height (SBH) and ideality factor, indicating the presence of SBH inhomogeneities at the Pt-Ga2O3 interface. Our results suggest that UV/O3 treatment tunes the SBH and its inhomogeneity. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis demonstrated a reduction in oxygen vacancies and a more uniform morphology of Ga2O3 thin films following the UV/O3 treatment. Consequently, the UV/O3-treated Pt/Ga2O3 SBDs showed a significant increase in the current on/off ratio, attributable to the improved interface quality due to reduced oxygen vacancy-related defects. UV/O3 surface treatment of Ga2O3 SBDs improved electrical performance through effective interface engineering.
The high breakdown electric field, n-type doping capability, availability of high-quality substrates, and high Baliga’s figure of merit of Ga2O3 demonstrate its potential as a next-generation power semiconductor material. However, the thermal conductivity of Ga2O3 is lower than that of other wide-bandgap materials, resulting in the degradation of the electrical performance and reduced reliability of devices. The heterostructure formation on substrates with high thermal conductivity has been noted to facilitate heat dissipation in devices. In this work, Ga2O3 thin films with an Al2O3 interlayer were deposited on SiC substrates by radio frequency sputtering. Post-deposition annealing was performed at 900 °C for 1 h to crystallize the Ga2O3 thin films. The Auger electron spectroscopy depth profiles revealed the interdiffusion of the Ga and Al atoms at the Ga2O3/Al2O3 interface after annealing. The X-ray diffraction (XRD) results displayed improved crystallinity after annealing and adding the Al2O3 interlayer. The crystallite size increased from 5.72 to 8.09 nm as calculated by the Scherrer equation using the full width at half maximum (FWHM). The carrier mobility was enhanced from 5.31 to 28.39 cm2 V−1 s−1 in the annealed Ga2O3 thin films on Al2O3/SiC. The transfer and output characteristics of the Ga2O3/SiC and Ga2O3/Al2O3/SiC back-gate transistors reflect the trend of the XRD and Hall measurement results. Therefore, this work demonstrated that the physical and electrical properties of the Ga2O3/SiC back-gate transistors can be improved by post-deposition annealing and the introduction of an Al2O3 interlayer.
We present a comparison between the thermal sensing behaviors of 4H-SiC Schottky barrier diodes, junction barrier Schottky diodes, and PiN diodes in a temperature range from 293 K to 573 K. The thermal sensitivity of the devices was calculated from the slope of the forward voltage versus temperature plot. At a forward current of 10 μA, the PiN diode presented the highest sensitivity peak (4.11 mV K −1 ), compared to the peaks of the junction barrier Schottky diode and the Schottky barrier diode (2.1 mV K −1 and 1.9 mV K −1 , respectively). The minimum temperature errors of the PiN and junction barrier Schottky diodes were 0.365 K and 0.565 K, respectively, for a forward current of 80 μA±10 μA. The corresponding value for the Schottky barrier diode was 0.985 K for a forward current of 150 μA±10 μA. In contrast to Schottky diodes, the PiN diode presents a lower increase in saturation current with temperature. Therefore, the nonlinear contribution of the saturation current with respect to the forward current is negligible; this contributes to the higher sensitivity of the PiN diode, allowing for the design and fabrication of highly linear sensors that can operate in a wider temperature range than the other two diode types.
We investigated the post annealing effect of Al implantation in n -type 4H-SiC by using deep level transient spectroscopy (DLTS). The Schottky contacts were deposited on n -type epitaxial layer on 4H-SiC substrates and the effect of Al-implantation on the structures has been examined with and without post-annealing process. n -type epitaxial layer on a 4H-SiC substrate was implanted with Al-ion at an energy of 300 keV and a dose of 1.0 × 10 15 cm –2 . The effect of annealing has been studied by annealing the structures at 1700 C after ion implantation. DLTS measurements were performed before and after ion implantation, in order to determine the characteristics and magnitudes of the resulting electrical defects. Based on the DLTS measurement results, typical Z 1/2 peak of SiC is obtained in reference samples without implantation. Z 1/2 of the non-annealed samples had an energy level of 0.831 eV. The energy level was found to be deeper after the implantation whereas the capture cross section is about 60 times smaller and the trap concentration increases by a factor of 10. In other words, the Al-ion implantation clearly influenced the electrical characteristics of the sample and consequently also the DLTS measurement results. After post-implantation annealing, a new shallow defect (I 2Al-A ) was identified (∼0.028 eV) with a capture cross section of 1.9 × 10 –21 cm –2 and a trap concentration of 4.8 × 10 15 cm –3 .
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