Fabrication of Si-based room temperature infrared light-emitting diodes using β-FeSi_2

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The purpose of this work is to fabricate infrared light-emitting diodes (LEDs) using semiconducting β-FeSi_2 which operate at room temperature (RT). In the term of this project, we have realized RT 1.6μm electroluminescence (EL) from p-Si/β-FeSi_2 particles/n-Si LEDs for the first time. It was found that the luminescence from β-FeSi_2 particles embedded in Si was very sensitive to the following growth conditions.1. The photoluminescence (PL) intensity of β-FeSi_2 strongly depends on MBE-Si growth temperature for embedding β-FeSi_2 in Si. When the Si overlayer was grown at lower temperatures of 400-500℃, the PL was intense. In contrast, the PL was very weak and was difficult to detect when it was grown at higher temperatures of 600-750℃. It was found that about 9% tensile strain was introduced into the particles in the [100] direction of β-FeSi_2, making the β-FeSi_2 a direct band gap semiconductor.2. PL was found to be sensitive to the size of β-FeSi_2 particles embedded in Si matrix. The PL intensity increased with the size of β-FeSi_2, but the intensity of 1.2-1.4μm broad PL also increased for samples with β-FeSi_2 bigger than 200nm. Transmission electron microscopy observation revealed that dislocations were introduced around the particles for those samples.3. PL was found to improve significantly by optimizing p-Si growth temperature and its boron concentration. Dislocation and point defects were found to be generated by oxygen incorporated in to the heavily boron-doped Si layer during the 14h of thermal annealing at 900℃, and are suggested to be responsible for the quenching of the PL.