Abstract
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//GaAs. 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//GaAs. 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 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).
Highlights
Single crystal rare earth (RE) oxides have been epitaxially grown on GaAs [1,2,3], Si [4,5,6,7], and GaN [8,9] using ultra-high vacuum (UHV) e-beam evaporation in a growth mode of molecular beam epitaxy (MBE) and atomic layer deposition (ALD)
From the reflection high energy electron diffraction (RHEED) and X-ray diffraction (XRD) studies, we found that the 2 nm thick ALD-Y2O3 grown on GaAs(111) is a cubic phase but has (111) normal
Single crystal rare earth oxide films were grown on GaAs(001) and GaAs(111)A using molecular beam epitaxy (MBE) and on GaAs(111) using ALD
Summary
Single crystal rare earth (RE) oxides have been epitaxially grown on GaAs [1,2,3], Si [4,5,6,7], and GaN [8,9] using ultra-high vacuum (UHV) e-beam evaporation in a growth mode of molecular beam epitaxy (MBE) and atomic layer deposition (ALD). ALD-LaLuO3 and -La2 ́xYxO3 on GaAs(111) were found to be of single crystal [3], showing CVs with a small dispersion at accumulation for both p- and n-GaAs(111) substrates and a low Dit [3], similar to what has been achieved earlier using the MBE-RE oxides on GaAs(001) [1,10,13].
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