Selective Growth of GaP Crystals on CMOS-Compatible Si Nanotip Wafers by Gas Source Molecular Beam Epitaxy.

Gallium phosphide (GaP) is a III-V semiconductor with remarkable optoelectronic properties, and it has almost the same lattice constant as silicon (Si). However, to date, the monolithic and large-scale integration of GaP devices with silicon remains challenging. In this study, we present a nanoheteroepitaxy approach using gas-source molecular-beam epitaxy for selective growth of GaP islands on Si nanotips, which were fabricated using complementary metal-oxide semiconductor (CMOS) technology on a 200 mm n-type Si(001) wafer. Our results show that GaP islands with sizes on the order of hundreds of nanometers can be successfully grown on CMOS-compatible wafers. These islands exhibit a zinc-blende phase and possess optoelectronic properties similar to those of a high-quality epitaxial GaP layer. This result marks a notable advancement in the seamless integration of GaP-based devices with high scalability into Si nanotechnology and integrated optoelectronics.

Field-Free Deterministic Magnetization Switching with Ultralow Current Density in Epitaxial Au/Fe4N Bilayer Films.

Current-induced magnetization switching was investigated in Au/Fe4N bilayer films grown by a plasma-assisted molecular beam epitaxy (PA-MBE) system. Depending on lattice distortion and interfacial coupling induced by substrates, the Fe4N layer could be divided into two sublayers having different magnetic anisotropies. The bottom sublayer shows perpendicular magnetic anisotropy (PMA), while the top one has in-plane magnetic anisotropy (IMA). Coupling between the two sublayers provides an extra in-plane effective field and enables a field-free magnetization switching in the bilayer films. By summarizing a series of Hall measurements, a switching phase diagram was obtained. Temperature-dependent switching behaviors demonstrate that the threshold current density for the field-free magnetization switching, which is much smaller than that of pervious reports, increases with decreasing temperature and shows similar temperature dependences to those of coercivity.

Charge Density Wave Phase Transitions in Large-Scale Few-Layer 1T-VTe2 Grown by Molecular Beam Epitaxy.

Charge density wave (CDW) as a novel effect in two-dimensional transition metal dichalcogenides (TMDs) has obtained a rapid rise of interest for its physical nature and potential applications in oscillators and memory devices. Here, we report var der Waals epitaxial growth of centimeter-scale 1T-VTe2 thin films on mica by molecular beam epitaxy. The VTe2 thin films showed sudden resistance change at temperatures of 240 and 135 K, corresponding to two CDW phase transitions driven by temperature. Moreover, the phase transitions can be driven by an electric field due to local Joule heating, and the corresponding resistance states are nonvolatile and controllable, which could be applied to the memory device where the logic states can be switched by an electric field. The multistage CDW phase transitions in the VTe2 thin films could be contributed to electron-phonon coupling in the two-dimensional VTe2, which is supported by twice pronounced Raman blue shifts of the vibration modes associated with in-plane phonons at CDW phase transition temperature. The results open up a new platform for understanding the microscopic physical essence and electrical control of CDW phases of TMDs, expanding the functionalities of these materials for memory applications.

Broad spectral response of an individual tellurium nanobelt grown by molecular beam epitaxy.

The detection of broad wavelengths from the near-ultraviolet to near-infrared regime using functional semiconductor nanostructures is of great importance in either fundamental research or technological application. In this work, we report high-performance optoelectronic nanodevices based on a single Te nanobelt grown by molecular beam epitaxy. The photodetector demonstrates a fast photoresponse time (a rise time of 510 µs and a decay time of 300 µs), a high photoresponsivity of 254.2 A W-1, an external quantum efficiency of 8.6 × 104%, a large detectivity of 8.3 × 108 Jones, on/off ratio of 3 orders, broadband response from the near-ultraviolet to near-infrared region, and robust photocurrent stability and reproducibility. The photodetector with superior performances based on the individual one-dimensional Te nanobelt consequently shows great promise for further optoelectronic device applications.