Helium-like impurity centers in silicon and germanium: Infrared light interaction, non-equilibrium distributions and optoelectronic applications

申请小组的共同目标是研究元素半导体、硅和锗中类氦杂质中心在中红外波长范围内光电子应用中的潜力。这类杂质的活化能落在红外光谱区。我们特别想研究硅中的双给体中心和锗中的双受体和三受体的光学、电光和磁光以及非平衡性质和动力学过程。这类材料的时间和光谱特性取决于一些基本特征，如掺杂后在半导体中形成的电活性中心的性质、所有活性杂质的激发态结构（包括它们的自旋轨道态和自旋三重态）、非平衡载流子的俘获和中心内弛豫。这些都不是已知的，也不是完全理解的材料。类氦杂质中心的最大中心跃迁能量超过了主晶格的光学声子的特征能量。预计这将减缓中心内弛豫，从而减缓整个捕获过程。此外，禁止的三重态-单线态衰变可能导致这些电子以这种三重态结束的弛豫时间很长。这些特征将通过双色时间分辨光谱进行实验研究，并建立理论模型。特别关注的是晶体生长和半导体掺杂的技术方面。

The joint goal of the applicant groups is to investigate the potential of helium-like impurity centers in the elemental semiconductors silicon and germanium for optoelectronic applications in the mid-infrared wavelength range. The activation energies of such impurities fall into the infarred spectral region. In particular, we want to study optical, electro-optical and magneto-optical as well as non-equilibrium properties and dynamical processes of double donor centers in silicon and double and triple acceptors in germanium. The temporal and spectral characteristics of such materials depend on fundamental features such as the nature of the electrically active centers formed in the semiconductor after doping, the structure of the excited levels of all active impurities, including their spin-orbit and spin-triplet states, the capture and intracenter relaxation of non-equilibrium charge carriers. These are not all known or not completely understood for the materials. The largest intracenter transitions of helium-like impurity centers have energies exceeding the characteristic energy of the optical phonon of the host lattice. This is expected to slow down the intracenter relaxation and, therefore, the whole capture process. Additionally, the forbidden triplet-singlet decay may result in long relaxation times for those electrons ending in such triplet states. These features will be experimentally investigated by two-color time-resolved spectroscopy and theoretically modelled. A special focus is on the technological aspects of crystal growth and doping of the semiconductors.