Al 2 O 3 was deposited on In 0.15 Ga 0.85 As/ GaAs using atomic-layer deposition ͑ALD͒. Without any surface preparation or postthermal treatment, excellent electrical properties of Al 2 O 3 / InGaAs/ GaAs heterostructures were obtained, in terms of low electrical leakage current density ͑10 −8 to 10 −9 A/cm 2 ͒ and low interfacial density of states ͑D it ͒ in the range of 10 12 cm −2 eV −1. The interfacial reaction and structural properties studied by high-resolution x-ray photoelectron spectroscopy ͑HRXPS͒ and high-resolution transmission electron microscopy ͑HRTEM͒. The depth profile of HRXPS, using synchrotron radiation beam and low-energy Ar + sputtering, exhibited no residual arsenic oxides at interface. The removal of the arsenic oxides from Al 2 O 3 / InGaAs heterostructures during the ALD process ensures the Fermi-level unpinning, which was observed in the capacitance-voltage measurements. The HRTEM shows sharp transition from amorphous oxide to single crystalline semiconductor.

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.

Ga 2 O 3 ( Gd 2 O 3 ) ∕ Ga As heterostructures have been annealed up to ∼780°C. Studies using x-ray reflectivity and high-resolution transmission electron microscopy have shown that the samples annealed under ultrahigh vacuum have maintained smooth and abrupt interfaces with the interfacial roughness being less than 0.2nm. The oxide remains amorphous, an important parameter for device consideration. Current–voltage and capacitance–voltage measurements have shown low leakage currents (10−8–10−9A∕cm2), a high dielectric constant of 15, and a low interfacial density of states (Dit) between gate dielectrics and GaAs. The attainment of a smooth interface between the gate dielectric and GaAs, even after high temperature annealing for activating implanted dopant, is a must to ensure the low (Dit) and to maintain a high carrier mobility in the channel of the metal–oxide–semiconductor field-effect transistor.

Articles you may be interested inHigh quality HfO2/p-GaSb(001) metal-oxide-semiconductor capacitors with 0.8nm equivalent oxide thickness Appl. Phys. Lett. 105, 222103 (2014); 10.1063/1.4903068 Modeling and analysis of the admittance characteristics of n+ metal-oxide-semiconductor capacitors with oxide and interface states -Gd0.25Ga0.15O0.6/Ga2O3 on In0.53Ga0.47AsLow interfacial trap density and sub-nm equivalent oxide thickness in In0.53Ga0.47As (001) metal-oxidesemiconductor devices using molecular beam deposited HfO2/Al2O3 as gate dielectrics Appl. Phys. Lett. 99, 042908 (2011); 10.1063/1.3617436Engineering of threshold voltages in molecular beam epitaxy-grown Al 2 O 3 ∕ Ga 2 O 3 ( Gd 2 O 3 ) ∕ In 0.2 Ga 0.8 As J.An equivalent oxide thickness about 1 nm for Ga 2 O 3 ͑Gd 2 O 3 ͒ ͑GGO͒ on In 0.2 Ga 0.8 As has been achieved by employing a thin in situ deposited 3 nm thick Al 2 O 3 protection layer. The dual gate oxide stacks of the Al 2 O 3 / GGO ͑33, 20, 10, 8.5, and 4.5 nm͒/In 0.2 Ga 0.8 As/ GaAs metal-oxide-semiconductor ͑MOS͒ capacitors remain amorphous after rapid thermal annealing up to 800-850°C, accompanied with atomically sharp smooth oxide/semiconductor interfaces. Well behaved capacitance-voltage ͑C-V͒ curves of the MOS diodes have shown sharp transition from depletion to accumulation with small flatband voltage ͑1.1 V for Au metal gate and 0.1 V for Al͒, and weak frequency dispersion ͑1.5%-5.4%͒ between 10 and 500 kHz at accumulation capacitance. Low leakage current densities ͓3.1ϫ 10 −5 and 2.5ϫ 10 −9 A / cm 2 at V = V fb + 1 V for Al 2 O 3 ͑3 nm͒ / GGO͑4.5 and 8.5 nm͔͒, a high dielectric constant around 14-16 of GGO for all tested thicknesses, and a low interfacial density of states ͑D it ͒ in the low 10 11 cm −2 eV −1 have also been accomplished.

Hexagonal-phase single-crystal Gd2 O3 is deposited on GaN in a molecular beam epitaxy system. The dielectric constant is about twice that of its cubic counterpart when deposited on InGaAs or Si. The capacitive effective thickness of 0.5 nm in hexagonal Gd2 O3 is perhaps the lowest on GaN-metal-oxide-semiconductor devices. The heterostructure is thermo dynamically stable at high temperatures and exhibits low interfacial densities of states after high-temperature annealing.