High In-containing long wavelength GaInN nanostructures on semi-polar surfaces

尽管氮化物半导体在光电子学中对于UV和蓝色光谱范围取得了巨大的成功，但是它们仍然遭受异质界面处的强压电场和GaInN层中的高铟掺入的问题，这限制了这些器件到目前为止向绿色或红色光谱范围的扩展。在“光发射器中的偏振场控制”研究小组中的这个项目中，我们希望通过在GaN纳米金字塔上沉积富In GaInN量子威尔斯来分别针对该绿色和红色光谱区域，所述GaN纳米金字塔通过选择性外延制造。这些金字塔的侧壁由半极性表面组成，使得在相应的GaN/GaInN界面处的电场将被强烈地降低。此外，与极性表面相比，更大量的铟可以嵌入在这些表面处。在第一个资助期内，我们专注于不同尺寸的微金字塔的制造和结构表征，以揭示绿色和橙红色光谱范围内发射的不同沉积条件。我们已经发现了预测的更高的In掺入和不同的载流子限制的金字塔上的区域。在项目的第二部分，我们特别专注于开发具有高铟含量的纳米金字塔作为有源区的LED结构。因此，我们必须一方面研究和控制In掺入，以实现红色光谱范围内的发射。另一方面，对于器件应用，我们必须完全过度生长样品。结合研究小组成员的其他活动，我们可以深入了解半极性表面上纳米结构的发射行为，并为绿色至红色光谱范围的活性区域的发展做出贡献。

In spite of the tremendous success of nitride semiconductors in optoelectronics for the UV and blue spectral range, they still suffer from strong piezoelectric fields at the heterointerfaces and problems with high indium incorporation in GaInN layers, which limits the extension of these devices to the green or red spectral range up to now. With this project within the research group “Polarization field control in light emitters” we like to target this green, respectively red spectral region, by depositing In-rich GaInN quantum wells on GaN nano-pyramids fabricated by selective epitaxy. The sidewalls of these pyramids consist of semi-polar surfaces so that the electric field at the corresponding GaN/GaInN interfaces will be strongly reduced. In addition, a larger amount of indium can be embedded at these surfaces as compared to polar surfaces. In the first funding period we have focused on the fabrication and the structural characterization of micro-pyramids of different sizes to reveal the different deposition conditions for emission in the green and orange-red spectral range. We have found the predicted higher In-incorporation and regions of different carrier confinement on the pyramid. In the second part of the project we especially concentrate on the development of LED structures with high Indium containing nano-pyramids as active region. Therefore, we have to investigate and control on one hand the In-incorporation to achieve emission in the red spectral range. On the other hand, for device applications, we have to overgrow the samples completely. In combination with the other activities of the research group members we can get deep insight into the emission behavior of nanostructures on semi-polar surfaces and contribute to the development of active regions for the green to red spectral range.