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N-polar AlGaN is an emerging wide-bandgap semiconductor for next-generation high electron mobility transistors and ultraviolet light emitting diodes and lasers. Here, we demonstrate the growth and characterization of high-quality N-polar AlGaN films on C-face 4H-silicon carbide (SiC) substrates by molecular beam epitaxy. On optimization of the growth conditions, N-polar AlGaN films exhibit a crack free, atomically smooth surface (rms roughness ∼ 0.9 nm), and high crystal quality with low density of defects and dislocations. The N-polar crystallographic orientation of the epitaxially grown AlGaN film is unambiguously confirmed by wet chemical etching. We demonstrate precise compositional tunability of the N-polar AlGaN films over a wide range of Al content and a high internal quantum efficiency ∼74% for the 65% Al content AlGaN film at room temperature. Furthermore, controllable silicon (Si) doping in high Al content (65%) N-polar AlGaN films has been demonstrated with the highest mobility value ∼65 cm2/V-s observed corresponding to an electron concentration of 1.1 × 1017 cm−3, whereas a relatively high mobility value of 18 cm2/V-s is sustained for an electron concentration of 3.2 × 1019 cm−3, with an exceptionally low resistivity value of 0.009 Ω·cm. The polarity-controlled epitaxy of AlGaN on SiC presents a viable approach for achieving high-quality N-polar III-nitride semiconductors that can be harnessed for a wide range of emerging electronic and optoelectronic device applications.

 

The anisotropic dielectric functions (DF) of corundum structuredm-planeα-(Al_xGa_1−x)₂O₃thin films (up tox= 0.76) grown onm-plane sapphire substrate by metalorganic CVD have been investigated. IR and visible–UV spectroscopic ellipsometry yields the DFs, while X-ray diffraction revealed the lattice parameters (a,m,c), showing the samples are almost fully relaxed. Analysis of the IR DFs from 250 to 6000 cm⁻¹by a complex Lorentz oscillator model yields the anisotropic IR active phononsE_uandA_2uand the shift towards higher wavenumbers with increasing Al content. Analyzing the UV DFs from 0.5 to 6.6 eV we find the change in the dielectric limitsε_∞and the shift of the Γ-point transition energies with increasing Al content. This results in anisotropic bowing parameters forα-(Al_xGa_1−x)₂O₃ofb_⊥= 2.1 eV andb_∣∣= 1.7 eV.

 

In this work, β-Ga 2 O 3 fin field-effect transistors (FinFETs) with metalorganic chemical vapor deposition grown epitaxial Si-doped channel layer on (010) semi-insulating β-Ga 2 O 3 substrates are demonstrated. β-Ga 2 O 3 fin channels with smooth sidewalls are produced by the plasma-free metal-assisted chemical etching (MacEtch) method. A specific on-resistance (R on,sp ) of 6.5 mΩ·cm 2 and a 370 V breakdown voltage are achieved. In addition, these MacEtch-formed FinFETs demonstrate DC transfer characteristics with near zero (9.7 mV) hysteresis. The effect of channel orientation on threshold voltage, subthreshold swing, hysteresis, and breakdown voltages is also characterized. The FinFET with channel perpendicular to the [102] direction is found to exhibit the lowest subthreshold swing and hysteresis. 

High crystalline quality thick β-Ga₂O₃drift layers are essential for multi-kV vertical power devices. Low-pressure chemical vapor deposition (LPCVD) is suitable for achieving high growth rates. This paper presents a systematic study of the Schottky barrier diodes fabricated on four different Si-doped homoepitaxial β-Ga₂O₃thin films grown on Sn-doped (010) and (001) β-Ga₂O₃substrates by LPCVD with a fast growth rate varying from 13 to 21  μm/h. A higher temperature growth results in the highest reported growth rate to date. Room temperature current density–voltage data for different Schottky diodes are presented, and diode characteristics, such as ideality factor, barrier height, specific on-resistance, and breakdown voltage are studied. Temperature dependence (25–250 °C) of the ideality factor, barrier height, and specific on-resistance is also analyzed from the J–V–T characteristics of the fabricated Schottky diodes.