Nanometer‐Thick Single‐Crystal Hexagonal Gd₂O₃ on GaN for Advanced Complementary Metal‐Oxide‐Semiconductor Technology

Abstract

Hexagonal-phase single-crystal Gd2 O3 is deposited on GaN in a molecular beam epitaxy system. The dielectric constant is about twice that of its cubic counterpart when deposited on InGaAs or Si. The capacitive effective thickness of 0.5 nm in hexagonal Gd2 O3 is perhaps the lowest on GaN-metal-oxide-semiconductor devices. The heterostructure is thermo dynamically stable at high temperatures and exhibits low interfacial densities of states after high-temperature annealing.

Epitaxial stabilization of a monoclinic phase in Y2O3 films on c-plane GaN

“…Among them, crystalline Gd 2 O 3 has effectively passivated GaAs surface, thus opening up a new era for GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) [7]. Moreover, a single crystal Gd 2 O 3 layer on GaN yielded a high dielectric constant of 24 with a low CET of 0.5 nm [13]. Previous work demonstrated that Y 2 O 3 passivates GaAs [9,17] and Ge [16] surface without the need of an interfacial layer.…”

“…Yttrium sesquioxide thus exhibits similar physical properties and has often been employed for the similar applications as rare-earth oxides. Gd 2 O 3 , La 2 O 3 , and Y 2 O 3 have been applied to GaAs [7][8][9][10], GaN [11][12][13], and Ge [14][15][16], respectively, as gate dielectrics for pursuing low capacitance equivalent thickness (CET) and high performance device. Among them, crystalline Gd 2 O 3 has effectively passivated GaAs surface, thus opening up a new era for GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) [7].…”

Growth and application of epitaxial heterostructures with polymorphous rare-earth oxides

“…Rare-earth oxides are also considered as a gate dielectric material [10][11][12] because of the combination of relatively wide bandgap and dielectric constant (subsequently, 5.9 eV and 14 for gadolinium oxide). Growth of Gd 2 O 3 on 6H-SiC leads to the formation of both monoclinic and cubic phases [11].…”

MBE—Enabling technology beyond Si CMOS

“…MBE deposited nm-thick hexagonal single crystal Gd 2 O 3 epitaxially on GaN [19] (Fig. 4(a) and (b)), a high-temperature phase at 42473 1C, stabilized with epitaxy at a lower deposition temperature, has a dielectric constant of $ 24 (Fig.…”

“…With the ability in atomically tailoring the high k's/semiconductor interfaces [17] and in epitaxy-stabilizing non-equilibrium phases with enhanced high k values [18,19], the in-situ MBE will continue to play a very critical role in addressing/solving the challenges of EOT, D it , and thermal stability at high temperatures. The multi-chamber system combines InGaAs, oxide, and metal MBE chambers, and other analysis chambers, such as X-ray photoelectron spectroscopy (XPS), and ultra high vacuum (UHV) transfer modules connecting these chambers ( Fig.…”