In this letter, we have investigated the physical and electrical characteristics of atomic layer deposition of HfO 2 on GaAs substrates. X-ray photoelectron spectroscopy ͑XPS͒ analysis revealed no significant reduction of arsenic oxides upon deposition of HfO 2 on GaAs using tetrakis͑dimethyl-amino͒hafnium ͓Hf͑NMe 2 ͒ 4 ͔ as the metallic precursor. However, XPS confirmed the absence of arsenic oxides at the interface of HfO 2 and sulfide-treated GaAs. High-resolution transmission electron microcopy analysis verified a smooth interface between HfO 2 and sulfur-passivated GaAs. In addition, frequency dispersion behavior of capacitors on p-type GaAs substrates was remarkably improved by employing an appropriate surface chemical treatment.
Electrical and physical characteristics of the atomic layer deposited beryllium oxide (BeO) grown on the Si and GaAs substrates were evaluated as a barrier/passivation layer in the III-V devices. Compared to Al2O3, BeO exhibits lower interface defect density and hysteresis, and smaller frequency dispersion and leakage current density at the same effective oxide thickness, as well as an excellent self-cleaning effect. These dielectric characteristics combined with its advantageous intrinsic properties, such as high thermal stability, large energy band-gap(10.6 eV), effective diffusion barrier, and low intrinsic structural defects, make BeO an excellent candidate for the interfacial passivation layer applications in the channel III-V devices.
In this letter, we report fabrication of self-aligned inversion-type enhancement-mode GaAs metal-oxide-semiconductor (MOS) field-effect transistors with atomic layer deposition of Al2O3 gate dielectric directly on GaAs substrates using a simple ex situ wet clean of GaAs. Thermal stability of the gate stack was examined by monitoring the frequency dispersion behavior of GaAs MOS capacitors under different annealing conditions. A maximum drive current of ∼4.5μA∕μm was obtained for a gate length of 20μm at a gate overdrive of 2.5V. The threshold voltage and subthreshold slope were determined to be ∼0.4V and ∼145mV∕dec from the corresponding Id-Vg characteristics.
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