We report on demonstrating high performance lateral β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) with source-connected field plate (FP) on a thin (150 nm) and highly Si-doped (n = 1.5 × 1018 cm−3) β-Ga2O3 epitaxial channel layer grown by ozone molecular beam epitaxy (MBE) on Fe-doped semi-insulating (010) substrate. For a MOSFET with a gate-drain spacing (Lgd) of 25 μm, the three terminal off-state breakdown voltage (VBR) tested in Fluorinert ambient reaches 2321 V. To the best of our knowledge, this is the first report of lateral β-Ga2O3 MOSFET with high VBR of more than 2 kV and the highest VBR attained among all the Ga2O3 MOSFETs. The breakdown voltages with different Lgd from 5–25 μm ranged from 518–2321V, with a linear trend of increasing breakdown voltage for larger spacing lateral MOSFETs. Combining with high electrical performances and excellent material properties, source-connected FP lateral β-Ga2O3 MOSFET implies its great potential for next generation high-voltage and high-power switching devices applications above 2 kV.
The impacts of SiN/Al 2 O 3 bi-layer passivation on the carrier transport characteristics in GaN-based metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) were studied. Various mechanical stresses, as measured by micro-Ramam spectroscopy, were introduced on the GaN channel according to the different passivation systems. The SiN dielectric layer deposited by plasma enhanced chemical vapor deposition on top of the GaN capping layer resulted in compressive stress. On the other hand, the Al 2 O 3 passivation layer deposited by atomic layer deposition on SiN layer generated tensile stress, which compensated the compressive stress produced by the SiN layer. The correlation between the applied mechanical stress induced by the deposited dielectric layers and device performance of the GaN-based HEMT was also investigated. When a slight tensile stress was applied on the GaN channel through the bi-layer passivation, the carrier transfer characteristics were improved in terms of carrier concentration at the AlGaN/GaN interface, as well as carrier mobility and sheet resistance compared to the high compressive stress condition. These results show that the mechanical stress engineering via optimized passivation process is a promising technique for the improvement of the device performance in GaN-based MISHEMTs.
Enhancement-mode (E-mode) Al 2 O 3 /AlGaN/GaN MISHEMTs were fabricated by shallow recess combined with CF 4 plasma treatment (SR/F) and deep recess (DR) to compare the effect of each process technique on the device performance. To prevent the device performance degradation induced by plasma damage during gate recess, the digital etch technique was employed. The fabricated E-mode devices have positively shifted threshold voltage, and exhibit lower transconductance (g m ) and saturation drain current than depletion-mode devices. Due to the CF 4 plasma damage during F-treatment, SR/F shows a sharp drop of g m curve and low saturation drain current. In contrast, DR presents broad g m and high saturation drain current. It is also revealed that the digital etch for gate recess exhibits an isotropic etch profile, consequently increasing the on-resistance. There is no remarkable difference between SR/F and DR in f T and f max , but DR has a better linearity over SR/F owing to the absence of plasma damage during F-treatment. This results reveal that the DR using digital etch is promising technique to obtain the high performance E-mode MISHEMTs compared to the F-treatment.
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