InGaN-based light-emitting diodes (LEDs) have higher luminescence efficiency than other materials used for the blue and green LEDs in spite of their relatively high dislocation density. Localization theory has been used to explain this phenomenon, but the direct observation of localization states in the InGaN active region has been rarely reported. In this paper, we propose an LED structure to obtain higher luminescence efficiency in the yellow-green LEDs and directly observe the transition of carriers between different localization states. The localization states were investigated and confirmed by temperature-dependent photoluminescence and excitation power-dependent photoluminescence. The value of the external quantum efficiency also exhibited a higher radiative efficiency of the quantum well with a higher degree of localization states. These results offer a promising means of realizing high-luminescence LEDs.

Plasma-enhanced atomic layer deposition was employed to grow aluminum nitride (AlN) thin films on Si (100), Si (111), and c-plane sapphire substrates at 250 °C. Trimethylaluminum and Ar/N₂/H₂ plasma were utilized as Al and N precursors, respectively. The properties of AlN thin films grown on various substrates were comparatively analyzed. The investigation revealed that the as-grown AlN thin films exhibit a hexagonal wurtzite structure with preferred c-axis orientation and were polycrystalline, regardless of the substrates. The sharp AlN/substrate interfaces of the as-grown AlN are indicated by the clearly resolved Kiessig fringes measured through X-ray reflectivity. The surface morphology analysis indicated that the AlN grown on sapphire displays the largest crystal grain size and surface roughness value. Additionally, AlN/Si (100) shows the highest refractive index at a wavelength of 532 nm. Compared to AlN/sapphire, AlN/Si has a lower wavelength with an extinction coefficient of zero, indicating that AlN/Si has higher transmittance in the visible range. Overall, the study offers valuable insights into the properties of AlN thin films and their potential applications in optoelectronic devices, and provides a new technical idea for realizing high-quality AlN thin films with sharp AlN/substrate interfaces and smooth surfaces.