Oxygen Incorporation in the Molecular Beam Epitaxy Growth of Sc_xGa_1−xN and Sc_xAl_1−xN

Abstract

Secondary‐ion mass spectrometry (SIMS) is used to determine impurity concentrations of carbon and oxygen in two scandium‐containing nitride semiconductor multilayer heterostructures: ScxGa1−xN/GaN and ScxAl1−xN/AlN grown by molecular beam epitaxy (MBE). In the ScxGa1−xN/GaN heterostructure grown in metal‐rich conditions on GaN–SiC template substrates with Sc contents up to 28 at%, the oxygen concentration is found to be below 1 × 1019 cm−3, with an increase directly correlated with the scandium content. In the ScxAl1−xN–AlN heterostructure grown in nitrogen‐rich conditions on AlN–Al2O3 template substrates with Sc contents up to 26 at%, the oxygen concentration is found to be between 1019 and 1021 cm−3, again directly correlated with the Sc content. The increase in oxygen and carbon takes place during the deposition of scandium‐alloyed layers.

Ferroelectric Nitride Heterostructures on CMOS Compatible Molybdenum for Synaptic Memristors

“…Overall, Sc and Al have uniform incorporation along the growth direction, with an Sc content of ∼0.2. However, a significant reduction of the N signal accompanied by the increasing oxygen (O) signal was observed near the surface, suggesting a native oxide [(ScAl)­O x ] layer with a thickness of a few nanometers formed on the top surface when exposed to air, which is mainly due to the large oxygen affinity of Sc and Al. , The slight oxygen signal in the Mo template and the ScAlN layer is from the surface oxidation after STEM specimen preparation.…”

“…To maximize the advantage of ferroelectric ScAlN and promote its applications from discrete devices to systems and even hybrid integrated circuits, it is essential to make it compatible with the mature complementary metal oxide semiconductor (CMOS) technologies, in which achieving single-crystalline ferroelectric ScAlN heterostructures on metal electrodes is highly desired. To date, however, sputter deposited films are generally polycrystalline with very limited material quality. , The realization of fully epitaxial, single-crystalline ferroelectric nitrides, e.g., ScAlN, on metal electrodes will provide unique opportunities in band gap/polarization engineering, interface/defect/doping control, , thermal management, and high yield mass production. − To date, however, the achievement of single-crystalline III-N semiconductors on metals has remained elusive due to severe lattice misalignment, highly reactive metallic surfaces, and lack of a highly orientated metal substrates/templates . Among the commonly used CMOS compatible metals, the high melting point (∼2160 °C), low thermal expansion coefficient (5 × 10 –6 °C −1 at 20 °C), and low electrical resistivity (5 × 10 –8 Ω·m) of molybdenum (Mo) make it an ideal metal in the CMOS fabrication process .…”

Semiconducting character of LaN: Magnitude of the bandgap and origin of the electrical conductivity

“…37 Rather, the negative formation energy indicates that substitutional O is a major source of unintentional impurities which could possibly lead to degenerate n-type doping for LaN. In comparison, rocksalt ScN and Sc-containing nitride alloys, compounds with similar chemistry as LaN, have been found to have negative formation energy for ON in defect calculations, 33 and O gets unintentionally incorporated during growth 38,39 and results in degenerate n-type doping. 40 Thus, an oxygen-free growth environment is necessary to prevent the undesired degenerate doping by substitutional O for LaN.…”

Dawn of nitride ferroelectric semiconductors: from materials to devices

“…Due to the large electronegativity difference between Sc and oxygen, Sc has a large oxygen affinity like Al, which therefore leads to a severe oxygen incorporation issue during ScAlN growth [94,105]. On the other hand, it is difficult to purify the rare-earth (RE) elements due to their special chemical properties.…”