By using an alumination process of Si3N4 at high temperature with aluminum flux irradiation for sufficient time, homogeneously N-polar and atomically smooth AlN film has been realized on silicon substrate with inversion domain suppressed to less than 3.0 × 106 cm−2 and root mean square surface roughness of ∼0.4 nm. A general interface model is proposed to explain the mechanism of polarity determination. The sharp AlN(0001)/Si(111) interface exhibits 5:4 coincidence domain matching, resulting in an almost fully relaxed AlN film.

Interface phonon modes that are generated by several atomic layers at the heterointerface play a major role in the interface thermal conductance for nanoscale high-power devices such as nitride-based high-electron-mobility transistors and light-emitting diodes. Here we measure the local phonon spectra across AlN/Si and AlN/Al interfaces using atomically resolved vibrational electron energy-loss spectroscopy in a scanning transmission electron microscope. At the AlN/Si interface, we observe various interface phonon modes, of which the extended and localized modes act as bridges to connect the bulk AlN modes and bulk Si modes and are expected to boost the phonon transport, thus substantially contributing to interface thermal conductance. In comparison, no such phonon bridge is observed at the AlN/Al interface, for which partially extended modes dominate the interface thermal conductivity. This work provides valuable insights into understanding the interfacial thermal transport in nitride semiconductors and useful guidance for thermal management via interface engineering.

The electron devices in which electrons do not collide with other particles or in which the collision probability is very small in the transport process can be theoretically regarded as general vacuum electron devices. General vacuum electron devices include microfabricated vacuum nano-electronic devices, which can work in atmosphere, and some solid-state electron devices with nanoscale channel for electrons whose material characteristics are close to those of vacuum channels. Vacuum nano-electron devices (e.g., nanotriodes) are expected to be the fundamental elements for high-speed, radiation-resistant large-scale vacuum integrated circuits. The solid-state electron devices with spin semiconductor materials, multiferroics or topological crystal insulators are quite different from traditional semiconductor devices and are expected to operate under novel principles. Understanding vacuum electron devices from a microcosmic perspective and understanding solid-state electron devices from a vacuum perspective will promote a union of vacuum electronics and microelectronics, as well as the formation and development of general vacuum electronics.

This paper reports on AlN epilayers with improved crystalline quality grown on silicon-on-insulators (SOIs) by plasma-assisted molecular beam epitaxy (PAMBE). The influences of the substrate on threading dislocation (TD) and surface morphology have been investigated. Two sets of wafers were grown on Si and SOI substrates with the same optimized growth parameters. An atomically smooth AlN epilayer was realized on an SOI substrate with reduced TD density compared to that on Si. This result is attributed to the stress release effect due to the lattice distortion in the top silicon layer of the SOI substrate.

We report an AlN epi-layer grown on sapphire by plasma-assisted molecular beam epitaxy with a thin interlayer structure. The effects of growth mode on threading dislocations (TDs) and surface morphology are studied. Then an interlayer structure grown under a V/III ratio of 1 is adopted to improve the AlN crystalline quality. By optimizing the thickness of the interlayer, the TD density and surface roughness can be reduced simultaneously.