Single-Crystal Y2O3 Epitaxially on GaAs(001) and (111) Using Atomic Layer Deposition

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(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).

Epitaxy from a Periodic Y–O Monolayer: Growth of Single-Crystal Hexagonal YAlO3 Perovskite

“…The in situ RHEED patterns upon the initial growth of ALD Y 2 O 3 on the GaAs(111)A revealed ordered and crystalline Y 2 O 3 from 3 to 10 cycles, similar to our earlier work reported in Ref. [ 23 ]. The bottom panels of Figure 2 c show sharp, streaky reconstructed RHEED patterns of the clean epi-GaAs(111)A-(2 × 2) with Kikuchi arcs.…”

“…The in situ RHEED patterns upon the initial growth of ALD Y 2 O 3 on the GaAs(111)A revealed ordered and crystalline Y 2 O 3 from 3 to 10 cycles, similar to our earlier work reported in Ref. [23].…”

“…Atomic layer deposition (ALD), having the advantages of self-limiting growth with an atomic accuracy and conformal coverage, has been used in industrial manufacturing, where many ALD films are amorphous oxides. ALD, nonetheless, has produced single-crystal rare-earth oxides on GaAs(001) [ 23 , 24 ], (111)A [ 23 , 25 , 26 ], and GaN [ 27 ]. MBE, a physical vapor deposition method, grows complex structures (including superlattices) by evaporating the constituents at the same time or sequentially.…”

Atomic Nature of the Growth Mechanism of Atomic Layer Deposited High-κ Y2O3 on GaAs(001)-4 × 6 Based on in Situ Synchrotron Radiation Photoelectron Spectroscopy

“…We specifically selected the system of ALD-Y 2 O 3 on freshly molecular beam epitaxy (MBE)-grown pristine GaAs(001)-4 × 6 because the oxide film orients itself along the surface normal (110), which shows a single-domain single-crystalline cubic phase. , Moreover, the interfacial trap density ( D it ) is low (<10 12 cm –2 eV –1 ), and the D it distribution within the GaAs band gap is flat without a peak bulge in the midgap . A similar 3 + oxide, such as Al 2 O 3 , fails to return with such excellent electric performances. − In situ synchrotron radiation photoelectron spectroscopy (SRPES) was used to study the interfacial electronic structure of the film in sub-ML thickness to bulk.…”

Yttrium oxide as a Q-switcher for the near-infrared erbium-doped fiber laser

“…By detecting the thickness difference between the material coverage area and the silicon substrate in Figure 1A, the exact thickness of Y 2 O 3 was estimated as 7 nm in Figure 1B. According to the definition of two-dimensional (2D) materials, the Y 2 O 3 used here can be considered as two dimensional [59,60]. Meanwhile, the surface morphology of Y 2 O 3 is shown in Figure 1C, which reveals the compactness and uniformity of the material surface.…”