Optical spectroscopy of the band formation and band structure of metastable semiconductor systems

本项目的目的是研究各种亚稳半导体合金及其异质结构的电子、振动和磁性能及其相互关系。在这些系统中，带隙工程可以通过加入几个百分点的等价杂质来强烈扰动宿主半导体来实现。在项目开始时，我们将重点关注这种新型半导体合金中最突出的成员：Ga（N,As）和（Ga,In）（N,As）。稍后我们还将研究较少研究的合金Ga（N，P）和（Ga,In）（N，P）。季元（Ga,In）（N,As）已被用作电信激光器和高效太阳能电池的活性材料。了解和控制这种合金的独特性能将大大改善这些设备。我们将研究随着阴离子取代的增加，带的形成和n诱导带与宿主带之间的相互作用，以及亚稳系统相变过程中带的变化。高压和磁场下的光谱学将用于研究这些合金中的电子和声子态。实验结果将对这些半导体中最近提出的能带形成的微观模型进行严格的测试。此外，我们将确定重要的能带结构参数，以便对能带结构进行类似kp的描述。这样的kp描述构成了包含这些合金的器件的增益建模的基础。此外，应确定所考虑的异质系统Ga(N,As)/GaAs, (Ga,In)(N,As)/GaAs, Ga(N，P)/GaP和（Ga,In）（N， P）/GaP的带偏移。显微光谱应使用，以获得四元化合物中不同带隙（但平均合金成分相同）区域的空间扩展信息。不同的带隙似乎与等价杂质的不同近邻环境有关。

The aim of the project is to study the electronic, vibronic, and magnetic properties and the correlations between them of various metastable semiconductor alloys and their heterostructures. In these systems band gap engineering can be achieved by perturbing strongly a host semiconductor by incorporating a few percent of an isovalent impurity. At the beginning of the project we will focus on the most prominent members of this new class of semiconductor alloys: Ga(N,As) and (Ga,In)(N,As). Later on we will also investigate the less studied alloys Ga(N,P) and (Ga,In)(N,P). The quaternary (Ga,In)(N,As) is already employed as active material for lasers in telecommunications and for high efficiency solar cells. Understanding and controlling the unique properties of this alloy will considerably improve these devices. We will study the band formation and the interaction between Ninduced and host-like bands with increasing anion substitution as well as the alteration of bands during the phase transitions of the metastable systems. Optical spectroscopy under high pressures and in magnetic fields will be used to study electron and phonon states in these alloys. The experimental results will yield stringent tests of the recently proposed microscopic models of the band formation in these semiconductors. In addition, we will determine important band structure parameters for a k.p-like description of the band structure. Such k.p descriptions form the basis of gain modelling in devices containing these alloys. Furthermore, the band offsets shall be determined for the heterosystems under consideration Ga(N,As)/GaAs, (Ga,In)(N,As)/GaAs, Ga(N,P)/GaP and (Ga,In) (N,P)/GaP. Micro-spectroscopy shall be used to obtain information about the spatial extension of the areas with different band gaps (but the same mean alloy composition) in the quaternary compounds. The different band gaps seem to be correlated to the different nearest-neighbour environments of the isovalent impurity.