•A HfO2/Al2O3 multilayer has been deposited by ALD technique on diamond.•The k value for HfO2/Al2O3 multilayer is larger than that for single ALD-Al2O3.•Fixed charge density of HfO2/Al2O3/H-diamond is lower than that of HfO2/H-diamond.•The ALD-HfO2/Al2O3/H-diamond MISFET shows good electrical properties.A HfO2/Al2O3 multilayer has been deposited by an atomic layer deposition (ALD) technique on a hydrogenated-diamond (H-diamond) epitaxial layer. Electrical properties of the ALD-HfO2/Al2O3/H-diamond metal-insulator-semiconductor (MIS) diode have been investigated to compare with those of the single ALD-Al2O3/H-diamond and ALD-HfO2/H-diamond MIS diodes. The leakage current density for the ALD-HfO2/Al2O3/H-diamond MIS diode is smaller than 3.8 × 10− 8 A·cm− 2 with electric field ranging from − 1.6 to 1.0 MV·cm− 1. The dielectric constant for the ALD-HfO2/Al2O3 multilayer is larger than that for the single ALD-Al2O3. The fixed charge density in the ALD-HfO2/Al2O3/H-diamond structure is much lower than that in the single ALD-HfO2/H-diamond structure. The electrical properties of the ALD-HfO2/Al2O3/H-diamond MIS field effect transistor have also been investigated. The source–drain current and extrinsic transconductance maxima are − 42.1 mA·mm− 1 and 6.2 ± 0.1 mS·mm− 1, respectively. The effective mobility for the H-diamond channel layer has been determined to be 38.2 ± 0.5 cm2·V− 1·s− 1.

Effects of nitrogen incorporation on the interface chemical bonding states, optical dielectric function, band alignment, and electrical properties of sputtering-derived HfTiO high-k gate dielectrics on GaAs substrates have been studied by angle resolved X-ray photoemission spectroscopy (ARXPS), spectroscopy ellipsometry (SE), and electrical measurements. XPS analysis has confirmed that the interfacial layer of a HfTiO/GaAs gate stack is suppressed effectively after nitrogen incorporation. Analysis by SE has confirmed that reduction in band gap and increase in refractive index are observed with the incorporation of nitrogen. Reduction in valence band offset and increase in conduction band offset have been observed for a HfTiON/GaAs gate stack. Electrical measurements based on metal-oxide-semiconductor (MOS) capacitors have shown that the MOS capacitor with a HfTiON/GaAs stacked gate dielectric annealed at 600 °C exhibits low interface-state density (2.8 × 1012 cm−2 eV−1), small gate leakage current (2.67 × 10−5 A cm−2 at Vg = Vfb + V), and large dielectric constant (25.8). The involved mechanisms may originate from the decrease in the interface state density and the increase in the conduction band offset. The appropriate band offset relative to GaAs and excellent interface properties render HfTiON/GaAs as promising gate stacks in future III–V-based devices.

GaN films with single-crystalline and polycrystalline structures were deposited by metalorganic chemical vapor deposition (MOCVD) on (111) and (100) MgAl2O4 substrates modified by chemical etching and thermal passivation. The oriented GaN films on the as-processed (111) MgAl2O4 substrate revealed broad visible emission band bands at 3.2 eV and a sharp luminescence peak centered at 1.8 eV in room temperature cathodoluminescence measurements, which can be attributed to the recombination of donor–acceptor pairs and GaN-related emission, respectively. Field emission (FE) measurements demonstrated that the oriented nanostructured 150 nm-thick GaN film on the as-processed (111) MgAl2O4 substrate has an ultralow turn-on-field of 4.29 V μm−1 at 10 nA cm−2 and a stable emission of 0.028 mA cm−2 with 5% current density fluctuation for 22 h without any degradation. Compared to GaN films on as-processed (100) MgAl2O4 substrate, the mechanism for the improved performance in optical and FE properties of the GaN film on as-processed (111) MgAl2O4 substrate has been investigated in detail.

•Ta2O5 has been deposited by a sputter-deposition technique at room temperature.•Electronic band configuration of Ta2O5/hydrogenated-diamond has been investigated.•Valence band offset has been found to be 1.5 ± 0.2 eV.•Large band offset makes it probably suitable for application of power devices.Ta2O5 films have been deposited on hydrogen-terminated diamond (H-diamond) by a radio-frequency sputter-deposition technique at room temperature. Electronic band structure of Ta2O5/H-diamond heterojunction has been investigated by X-ray photoelectron spectroscopy. Based on the binding energies of core-levels and valence band maximum values, valence band offset has been found to be 1.5 ± 0.2 eV for the Ta2O5/H-diamond heterointerface. It shows a type-II band configuration with conduction band offset of 2.4 ± 0.2 eV. The large ΔEV value makes the Ta2O5/H-diamond heterojunction probably suitable for the application of high power and high frequency field effect transistors.

Effects of nitrogen incorporation on the interface chemical bonding states, optical dielectric function, band alignment, and electrical properties of sputtering-derived HfTiO high-k gate dielectrics on GaAs substrates have been studied by angle resolved X-ray photoemission spectroscopy (ARXPS), spectroscopy ellipsometry (SE), and electrical measurements. XPS analysis has confirmed that the interfacial layer of a HfTiO/GaAs gate stack is suppressed effectively after nitrogen incorporation. Analysis by SE has confirmed that reduction in band gap and increase in refractive index are observed with the incorporation of nitrogen. Reduction in valence band offset and increase in conduction band offset have been observed for a HfTiON/GaAs gate stack. Electrical measurements based on metal-oxide-semiconductor (MOS) capacitors have shown that the MOS capacitor with a HfTiON/GaAs stacked gate dielectric annealed at 600 °C exhibits low interface-state density (2.8 × 1012 cm−2 eV−1), small gate leakage current (2.67 × 10−5 A cm−2 at Vg = Vfb + V), and large dielectric constant (25.8). The involved mechanisms may originate from the decrease in the interface state density and the increase in the conduction band offset. The appropriate band offset relative to GaAs and excellent interface properties render HfTiON/GaAs as promising gate stacks in future III–V-based devices.

GaN films with single-crystalline and polycrystalline structures were deposited by metalorganic chemical vapor deposition (MOCVD) on (111) and (100) MgAl2O4 substrates modified by chemical etching and thermal passivation. The oriented GaN films on the as-processed (111) MgAl2O4 substrate revealed broad visible emission band bands at 3.2 eV and a sharp luminescence peak centered at 1.8 eV in room temperature cathodoluminescence measurements, which can be attributed to the recombination of donor–acceptor pairs and GaN-related emission, respectively. Field emission (FE) measurements demonstrated that the oriented nanostructured 150 nm-thick GaN film on the as-processed (111) MgAl2O4 substrate has an ultralow turn-on-field of 4.29 V μm−1 at 10 nA cm−2 and a stable emission of 0.028 mA cm−2 with 5% current density fluctuation for 22 h without any degradation. Compared to GaN films on as-processed (100) MgAl2O4 substrate, the mechanism for the improved performance in optical and FE properties of the GaN film on as-processed (111) MgAl2O4 substrate has been investigated in detail.