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

本工作的目的是利用室温下工作的半导体β-FeSi_2制备红外发光二极管（led）。本课题首次实现了p-Si/β-FeSi_2粒子/n-Si led的RT - 1.6μm电致发光（EL）。结果表明，包埋在Si中的β-FeSi_2粒子的发光对以下生长条件非常敏感：β-FeSi_2的光致发光强度与MBE-Si生长温度密切相关。在400 ~ 500℃较低温度下生长Si覆盖层时，PL强烈。而在600 ~ 750℃的高温下生长时，荧光极弱，难以检测。结果表明，β-FeSi_2在[100]方向上引入了9%左右的拉伸应变，使β-FeSi_2成为直接带隙半导体。结果表明，PL对嵌入在Si基体中的β-FeSi_2颗粒的大小非常敏感。随着β-FeSi_2尺寸的增大，发光强度增大，但当β-FeSi_2尺寸大于200nm时，1.2 ~ 1.4μm宽的发光强度增大。透射电镜观察显示，这些样品的颗粒周围引入了位错。通过优化p-Si的生长温度和硼的浓度，可以显著提高PL。在900℃高温退火14h时，重硼掺杂的Si层中加入了氧气，产生了位错和点缺陷，这可能是导致PL猝灭的原因。

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.