High-Temperature Annealing of Si-Doped AlGaN

This study explores the impact of Si doping on the material properties of high-temperature annealed (HTA) Al0.71Ga0.29N layers, which are grown on AlN/sapphire templates. The AlGaN layers are doped with Si by applying different IV/III ratios during epitaxial growth and compared to undoped Al0.71Ga0.29N. Before HTA, the threading dislocation density (TDD) for all samples is about 6.0 x 109 cm-2. After HTA, the Si-doped AlGaN grown with the highest IV/III ratio of 3.6 x 104 shows the lowest TDD of 1.2 x 109 cm-2. Secondary ion mass spectrometry depth profiles reveal an accelerated Ga diffusion from the doped AlGaN into the AlN buffer layer compared to undoped AlGaN. This suggests that the Ga diffusion process is mediated by Si diffusion. Consequently, the Ga diffusion leads to a decrease in the Ga mole fraction of annealed Si-doped AlGaN. Furthermore, strain relaxation is higher for the Si-doped AlGaN than for the undoped AlGaN, before and after HTA. The results from this study suggest that Si doping can be a new promising approach in enhancing the quality of HTA-AlGaN as a useful template for the growth of UV LED heterostructures. Si doping significantly reduces threading dislocation density in high-temperature annealed AlGaN, especially with higher concentrations or IV/III ratios. The Si doping increases the number of vacancies and tiny pits size, facilitating Ga diffusion and removal during the annealing, further reducing the threading dislocation. Additionally, Si doping accelerates the Ga diffusion from the AlGaN into the AlN buffer layer.image (c) 2024 WILEY-VCH GmbH