Single-Crystal Y(2)O(3) Epitaxially on GaAs(001) and (111) Using Atomic Layer Deposition

Single-crystal atomic-layer-deposited (ALD) Y(2)O(3) 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 Y(2)O(3) films are of a cubic phase and have (110) as the film normal, with the orientation relationship being determined: Y(2)O(3) [Formula: see text] //GaAs [Formula: see text]. On GaAs(111)A, the Y(2)O(3) films are also of a cubic phase with (111) as the film normal, having the orientation relationship of Y(2)O(3) [Formula: see text] //GaAs [Formula: see text]. The relevant orientation for the present/future integrated circuit platform is (001). The ALD-Y(2)O(3)/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 (D(it)) is low of [Formula: see text] cm(−2)eV(−1) as extracted from measured quasi-static CVs. The frequency dispersion at accumulation and the D(it) are the lowest ever achieved among all the ALD-oxides on GaAs(001).