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Direct epitaxial integration of magnetic layers with wide bandgap nitride semiconductors will enable spin-controlled transport and photonic phenomena, seeding ideas for functional spintronic devices. Using plasma-assisted molecular beam epitaxy (MBE) in a previously unexplored window, significantly improved ferrimagnetic Mn4N layers are successfully grown on GaN with ~ 1 nm surface roughness. Distinct from earlier reports, the Mn4N layers grown on GaN are found to be 001 oriented with 12-fold in-plane symmetry in the diffraction pattern. This unique epitaxial registry originates from three equivalent rotational domains. The ferrimagnetic magnetotransport properties of low growth temperature Mn4N layers on GaN are comparable to those reported on cubic substrates such as MgO. However, a sign-flip of the Hall resistance is discovered for Mn4N layers grown above 300 °C.

Power and RF electronics applications have spurred massive investment into a range of wide and ultrawide bandgap semiconductor devices which can switch large currents and voltages rapidly with low losses. However, the end systems using these devices are often limited by the parasitics of integrating and driving these chips from the silicon complementary metal–oxide-semiconductor-based design (CMOS) circuitry necessary for complex control logic. For that reason, implementation of CMOS logic directly in the wide bandgap platform has become a way for each maturing material to compete. This review examines potential CMOS monolithic and hybrid approaches in a variety of wide bandgap materials.

A strong need exists for a wide-bandgap p-type transistor counterpart of the n-channel GaN HEMTs for power electronics and novel RF circuits. In this work, the first p-channel nitride transistors that break the GHz speed barrier are demonstrated. By leveraging the unique single-channel high-density polarization-induced 2D hole gas of the GaN/AlN heterostructure, best-in-class contact resistances, and scaled T-gate design, p-channel transistor on-currents of 428 mA/mm are observed, with cutoff frequencies in the 20 GHz regime. These observations demonstrate the unique enabling role of the polarization discontinuity at the GaN/AlN semiconductor heterojunction and offer significant hope for a new high-speed and high-voltage wide-bandgap CMOS device platform for applications in RF and power electronics domains.

Epitaxial multilayer heterostructures of ScxAl1−xN/GaN with Sc contents x = 0.11–0.45 are found to exhibit significant differences in structural quality, chemical impurity levels, and electronic properties depending on the starting Sc source impurity levels. A higher purity source leads to a 2–3 orders of magnitude reduction in the carbon, oxygen, and fluorine unintentional doping densities in MBE-grown ScxAl1−xN/GaN multilayers. Electrical measurements of ScxAl1−xN/n+GaN single heterostructure barriers show a 5–7 orders of magnitude reduction in the electrical leakage for films grown with a higher purity Sc source at most Sc contents. The measured chemical and electrical properties of epitaxial ScxAl1−xN highlight the importance of the starting Sc source material purity for epitaxial device applications that need these highly piezoelectric and/or ferroelectric transition-metal nitride alloys.

Nitride-based semiconductors have received considerable attention during the last decade due to their outstanding properties for optoelectronic, high frequency, and high power applications. The integration of GaN and Si (100) devices on the same chip would enable a vast array of new applications, from novel power distribution schemes in Si microsystems, to power digital-toanalog converters and new opportunities for optoelectronic devices integrated on a Si platform. This paper aims to summarize some of the recent results on the heterogeneous integration of GaN and Si (100) devices and circuits by using a hybrid 4" wafer bonding technology.

Back-gated MoSe2 thin-film transistors (TFTs) with an Al2O3-capping layer were fabricated, and the device characteristics of the MoSe2 TFTs that are dependent on the Al2O3-capping-layer passivation were investigated. The output drain current was doubled, the fluctuation of the output current was suppressed, and the threshold voltage of the MoSe2 TFTs was negatively shifted with the Al2O3-capping layer. The on/off-current ratio of the MoSe2 TFTs is approximately six decades regardless of the Al2O3-capping layer, but the field-effect mobility was greatly increased from 2.86 cm2/Vs to 10.26 cm2/Vs after the deposition of the Al2O3-capping layer. According to the results of this study, the Al2O3-capping layer can enhance the device characteristics of MoSe2 TFTs.

We investigated the dependence of electron mobility on the thickness of MoS2 nanosheets by fabricating bottom-gate single and few-layer MoS2 thin-film transistors with SiO2 gate dielectrics and Au electrodes. All the fabricated MoS2 transistors showed on/off-current ratio of similar to 10(7) and saturated output characteristics without high-k capping layers. As the MoS2 thickness increased from 1 to 6 layers, the field-effect mobility of the fabricated MoS2 transistors increased from similar to 10 to similar to 18 cm(2)V(-1)s(-1). The increased subthreshold swing of the fabricated transistors with MoS2 thickness suggests that the increase of MoS2 mobility with thickness may be related to the dependence of the contact resistance and the dielectric constant of MoS2 layer on its thickness. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).