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

尽管氮化物半导体在紫外光和蓝光波段的光电子学方面取得了巨大的成功，但它们仍然受制于异质界面上的强压电场和GaInN层中高In掺杂的问题，这限制了这些器件到目前为止在绿色或红色光谱范围内的扩展。随着这个课题组“光发射体中偏振场的控制”，我们希望通过在选择性外延制备的GaN纳米金字塔上沉积富In的GaInN量子阱来瞄准这个绿色的、分别是红色的光谱区域。这些金字塔的侧壁由半极表面组成，因此对应的GaN/GaInN界面上的电场将被强烈地降低。此外，与极性表面相比，在这些表面上可以嵌入更多的铟。在第一个资助期，我们重点研究了不同大小的微金字塔的制备和结构表征，以揭示在绿色和橙红色光谱范围内发射的不同沉积条件。我们在金字塔上发现了预期的较高的掺入和不同载流子限制的区域。在项目的第二部分，我们特别关注以高铟纳米金字塔为有源区的LED结构的开发。因此，我们一方面要研究和控制掺入，以实现在红光范围内的发射。另一方面，对于设备应用，我们必须完全过度增长样本。结合课题组成员的其他活动，我们可以深入了解半极性表面纳米结构的发射行为，并为开发绿色到红色光谱范围的活动区域做出贡献。

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.