Single-crystal atomic-layer-deposited (ALD) Y2O3 films 2 nm thick were epitaxially grown on molecular beam epitaxy (MBE) GaAs(001)-4 × 6 and GaAs(111)A-2 × 2 reconstructed surfaces. The in-plane epitaxy between the ALD-oxide films and GaAs was observed using in-situ reflection high-energy electron diffraction in our uniquely designed MBE/ALD multi-chamber system. More detailed studies on the crystallography of the hetero-structures were carried out using high-resolution synchrotron radiation X-ray diffraction. When deposited on GaAs(001), the Y2O3 films are of a cubic phase and have (110) as the film normal, with the orientation relationship being determined: Y2O3(110)[001][true1¯10]//GaAs(001)[110][1true1¯0]. On GaAs(111)A, the Y2O3 films are also of a cubic phase with (111) as the film normal, having the orientation relationship of Y2O3(111)[2true1¯true1¯][01true1¯]//GaAs(111)[true2¯11][0true1¯1]. The relevant orientation for the present/future integrated circuit platform is (001). The ALD-Y2O3/GaAs(001)-4 × 6 has shown excellent electrical properties. These include small frequency dispersion in the capacitance-voltage (CV) curves at accumulation of ~7% and ~14% for the respective p- and n-type samples with the measured frequencies of 1 MHz to 100 Hz. The interfacial trap density (Dit) is low of ~1012 cm−2eV−1 as extracted from measured quasi-static CVs. The frequency dispersion at accumulation and the Dit are the lowest ever achieved among all the ALD-oxides on GaAs(001).
Because
the dielectric constant (K), the leakage
current density (J
g), and the interfacial
state density (D
it) are critical to high-K gate dielectrics, the layer-by-layer, in situ atomic layer bombardment (ALB) is proposed and explored to enhance
these electrical properties in this study. The in situ helium/argon plasma bombardment was performed layer-by-layer in
each cycle of atomic layer deposition (ALD) for preparing high-K gate dielectrics. As compared with the untreated high-K layer, the ALB treatment contributes to a significant
reduction in J
g by ∼3 orders of
magnitude, together with an ∼11% increase of K value and a decrease of D
it, of high-K gate dielectrics. The suppressed J
g and the enhanced K value are ascribed to
an increase of film density and a decrease of oxygen vacancies in
the ZrO2 layer by the ALB treatment. The atomic annealing
effect due to the ALB technique contributes to the decrease of D
it. The result demonstrates that the ALD together
with the ALB technique is highly effective to further enhance the
dielectric properties of nanoscale thin films, which is important
and applicable in a variety of fields including nanoelectronic, energy-saving,
and biomedical devices.
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