We report the growth of high-quality AlN films on nano-patterned sapphire substrates (NPSSs) by graphene-assisted quasi-van der Waals epitaxy, which enables rapid coalescence to shorten the growth time. Due to the presence of graphene (Gr), AlN tends to be two-dimensional laterally expanded on the NPSS, leading to the reduction of dislocation density and strain release in the AlN epitaxial layer. Using first-principles calculations, we confirm that Gr can reduce the surface migration barrier and promote the lateral migration of metal Al atoms. Furthermore, the electroluminescence results of deep ultraviolet light emitting diodes (DUV-LEDs) have exhibited greatly enhanced emission located at 280 nm by inserting the Gr interlayer. The present work may provide the potential to solve the bottleneck of high efficiency DUV-LED.

We report the synthesis of CH₃NH₃Pb(Br_3−yX_y) (X=Cl and I) single crystals via a stepwise temperature control approach. High-quality CH₃NH₃Pb(Br_3−yX_y) crystals with a tunable bandgap from 1.92eV to 2.53eV have been prepared successfully in this way. And further experiments revealed the influence of halogen content and preparation temperature on the structural and optical properties of these crystals. It is observed that chlorine can lower the critical nucleation energy, which results in crystallizing at lower temperature with the chlorine content increasing, while the nucleation energy increases slowly with increasing iodine content. Moreover, in contrast to Frank–van der Merwe growth with low heating rate, high heating rate leads to a mass of small size single crystals and Stranski-Krastanov growth. The single crystals with tunable band gap and impressive characteristics enable us to fabricate high performance photodetectors for different wavelengths.

Understanding thermal transport mechanisms across material interfaces is crucial for advancing semiconductor technologies, particularly in miniaturized devices operating under extreme power densities ^1,2 . Although the interface phonon-mediated processes are theoretically established ^3–6 as the dominant mechanism for interfacial thermal transport in semiconductors ⁷ , their nanoscale dynamics remain experimentally elusive owing to challenges in measuring the temperature and non-equilibrium phonon distributions across the buried interface ^8–11 . Here we overcome these limitations by using in situ vibrational electron energy-loss spectroscopy (EELS) in an electron microscope to nanoscale profile temperature gradients across the AlN–SiC interface during thermal transport and map its non-equilibrium phonon occupations at sub-nanometre resolution. We observe a sharp temperature drop within about 2 nm across the interface, enabling direct extraction of relative interfacial thermal resistance (ITR). During thermal transport, the mismatch of phonon modes’ thermal conductivity at the interface causes substantial non-equilibrium phonons nearby, making the populations of interface modes different under forward and reverse heat flow and also leading to marked changes in the modal temperature of AlN optical phonons within about 3 nm of the interface. These results reveal the phonon transport dynamics at the (sub-)nanoscale and establish the inelastic phonon scattering mechanism involved by interface modes, offering valuable insights into the engineering of thermal interfaces.

The heteroepitaxy of nitride semiconductors can be achieved without needing lattice matching between two material systems.

Augmented reality (AR) is emerging as a next-generation interactive display that promotes the interaction between users, digital content, and the real world. Although micro-LED is regarded as the most promising light engine candidate for AR, its inherent Lambertian radiation characteristics and relatively broader emission spectrum result in low optical coupling efficiency and diffraction dispersion-related “rainbow” phenomenon when combined with a waveguide combiner. Here, we numerically and experimentally demonstrate resonant cavity (RC) micro-LEDs by incorporating SiO₂/TiO₂ distributed Bragg reflectors with chip sizes of 60, 100, and 150 μm. The device has a divergence angle of 78.7° and a narrow spectrum width of 6.8 nm, which is significantly lower than that of the controlled micro-LEDs. The reported GaN-based RC micro-LEDs have the potential to be used in the display panel for AR applications in a variety of scenarios, including AR glasses, and head up display for cars and airplanes.