Self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors (MOSFETs) using ultrahigh-vacuum deposited Al2O3∕Ga2O3(Gd2O3) (GGO) dual-layer dielectrics and a TiN metal gate were fabricated. For a In0.53Ga0.47As MOSFET using a gate dielectric of Al2O3(2nmthick)∕GGO(5nmthick), a maximum drain current of 1.05A∕mm, a transconductance of 714mS∕mm, and a peak mobility of 1300cm2∕Vs have been achieved, the highest ever reported for III-V inversion-channel devices of 1μm gate length.

High HfO 2 was deposited on n-type GaN ͑0001͒ using atomic layer deposition with Hf͑NCH 3 C 2 H 5 ͒ 4 and H 2 O as the precursors. Excellent electrical properties of TiN / HfO 2 / GaN metal-oxide-semiconductor diode with the oxide thickness of 8.8 nm were obtained, in terms of low electrical leakage current density ͑ϳ10 −6 A/cm 2 at V FB +1 V͒, well behaved capacitance-voltage ͑C-V͒ curves having a low interfacial density of states of 2 ϫ 10 11 cm −2 eV −1 at the midgap, and a high dielectric constant of 16.5. C-V curves with clear accumulation and depletion behaviors were shown, along with negligible frequency dispersion and hysteresis with sweeping biasing voltages. The structural properties studied by high-resolution transmission electron microscopy and x-ray reflectivity show an atomically smooth oxide/GaN interface, with an interfacial layer of GaON ϳ1.8 nm thick, as probed using x-ray photoelectron spectroscopy.

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Atomic-layer-deposited Al2O3 on In0.53Ga0.47As with short air exposure between the oxide and semiconductor deposition has enabled the demonstration of nearly ideal frequency-dependent and quasistatic capacitance-voltage (C-V) characteristics. The excellent quasistatic C-V characteristics indicate a high efficiency of 63% for the Fermi-level movement near the midgap. A low mean interfacial density of states (D¯it)∼2.5×1011 cm−2 eV−1 was determined under 1 MHz using a charge pumping method, which was also employed to probe the depth profile of bulk traps (Nbt) and the energy dependence of Dit at 50 kHz: a low Nbt∼7×1018 cm−3 and a Dit of (2–4)×1011 cm−2 eV−1 in the lower half of the band gap and a higher Dit of ∼1012 cm−2 eV−1 in the upper half of the band gap. The employment of charge pumping method has given a more accurate determination of Dit, which is usually overestimated using other commonly methods such as the Terman, conductance, and high-low frequencies due to the influence of weak inversion at room temperature.

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The pronounced high interfacial densities of states (Dit) commonly observed around the midgap energy of dielectric/GaAs interfaces are generally considered the culprit responsible for the poor electrical performance of the corresponding inversion-channel metal-oxide-semiconductor field-effect-transistors. In this work, comprehensive Dit spectra as the function of energy [Dit(E)] inside the In0.2Ga0.8As band gap were constructed by using the quasistatic capacitance-voltage and the temperature-dependent conductance method on n- and p-type ultrahigh vacuum (UHV)-Ga2O3(Gd2O3)/In0.2Ga0.8As and atomic-layer-deposited (ALD)-Al2O3/In0.2Ga0.8As metal-oxide-semiconductor capacitors. Unlike the ALD-Al2O3/In0.2Ga0.8As interface giving a Dit spectrum with a high midgap Dit peak, the UHV-Ga2O3(Gd2O3)/In0.2Ga0.8As interface shows a Dit spectrum that monotonically decreases from the valence band to the conduction band with no discernible midgap peak.

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