Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 34: Nitrides: Dots, rods, and structures
HL 34.6: Vortrag
Dienstag, 17. März 2015, 12:30–12:45, EW 201
Structural and optical properties of a GaN-bulk semi-microcavity structure — •Alexander Reuper, Gordon Schmidt, Peter Veit, Frank Bertram, Silke Petzold, Christoph Berger, Armin Dadgar, Alois Krost, André Strittmatter, and Jürgen Christen — Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany
Using transmission electron microscopy combined with cathodoluminescence spectroscopy (STEM-CL) we analyze structural and spatially resolved optical properties of a GaN-based bulk semi-microcavity structure.
The sample has been grown by metal-organic vapor phase epitaxy on a c-plane Al2O3 substrate. A lattice matched 45 pair AlInN/AlGaN distributed Bragg reflector (DBR) serves as bottom mirror for the GaN emission. As active medium consists the whole GaN-bulk cavity which ensures the complete overlap with the cavity mode.
Within the buffer structure, dislocation reduction by a SiN mask is found, whereas low temperature AlN layers, intended for stress control, generate new threading dislocations. In the DBR structure high resolution TEM images show the formations of thin AlN interlayers located at AlInN-AlGaN interfaces, indicating In desorption. Highly spatially resolved STEM-CL at 15 K exhibits GaN-NBE emission at 356 nm, corresponding to compressive strain of about 0.3 GPa. Furthermore, we observe a continuous redshift of GaN-NBE luminescence in growth direction from 356.5 nm at the cavity/DBR interface to 356.9 nm at the surface, indicating elastic relaxation of the GaN cavity.