Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 80: GaN: Preparation and Characterization V (mainly Cathodoluminescence)

HL 80.4: Vortrag

Donnerstag, 29. März 2012, 12:00–12:15, ER 270

Optical and Structural Properties of an AlInN/AlGaN Distributed Bragg Reflector using Scanning Transmission Electron Microscopy Cathodoluminescence — •Gordon Schmidt, Peter Veit, Alexander Franke, Frank Bertram, Jürgen Christen, Christoph Berger, Armin Dadgar, and Alois Krost — Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany

We present a direct nano-scale correlation of the optical properties and crystalline real structure of a lattice matched distributed Bragg reflector (DBR) using cathodoluminescence spectroscopy (CL) in a scanning transmission electron microscope (STEM).

The structure was grown by metal organic vapor phase epitaxy on sapphire substrate using an optimized buffer. The highly reflective DBR consits of 35 periods of AlInN and AlGaN λ/4 layers and is capped by a 200 nm thick 3λ/2 GaN cavity. The STEM-CL images clearly resolve the complete sequence of the DBR structure.

The Al_0.2Ga_0.8N buffer layers emit intense CL at a wavelength of 318 nm. The DBR layers are laterally and vertically homogeneous with sharp AlInN/AlGaN interfaces. Local spectra show a blueshift of the DBR emission from 327 nm to 323 nm in growth direction. The direct comparison of the STEM image with the simultaneously recorded monochromatic CL mapping of the DBR luminescence clearly identifies the AlGaN/AlInN interfaces as the origin of this emission. This indicates the formation of a 2D electron gas in the polarization field induced potential well at these interfaces.