GaN nanocolumns
The self-organized formation of GaN nanoclumns offers the unique possibility to fabricate strain- and defect-free GaN crystals on foreign substrates. The excellent structural as well as optical quality and the potential for a monolithic integration with Si is expected to lead to the realization of highly efficient emitters in the visible spectral range on Si.
The high crystal quality realized in this approach manifests itself in the narrow linewidth and high intensity of the spontaneous emission from these nanostructures. We are focusing our interest on the spectroscopic investigation of single, isolated GaN nanocolumns by micro-photoluminescence (µ-PL) and cathodoluminescence spectroscopy to obtain a detailed understanding of the properties of these nanostructures [1,2]. In particular, the impact of the free surface and the characteristics of the remaining structural defects are not fully understood to date.
The figures show a single GaN nanocolumn (top), which has been dispersed on Si, and the corresponding µ-PL spectrum (bottom). Both the spectral position and the width of the donor-bound exciton line visible in the spectrum indicate that the column, which had been unstrained as-grown, has become strained by the interaction with the underlying Si wafer.
- C. Rivera, U. Jahn, T. Flissikowski, J. L. Pau, E. Muñoz, and H. T. Grahn,
Strain-confinement mechanism in mesoscopic quantum disks based on piezoelectric materials,
Phys. Rev. B 75, 045316 (2007). - U. Jahn, J. Ristić, and E. Calleja,
Cathodoluminescence spectroscopy and imaging of GaN/(Al,Ga)N nanocolumns containing quantum disks,
Appl. Phys. Lett. 90, 161117 (2007).
