Spectroscopic study of semipolar (1122)-HVPE GaN exhibiting high oxygen incorporation.

Spatially resolved luminescence and Raman spectroscopy investigations are applied to a series of (1122)-GaN samples grown by hydride vapor phase epitaxy (HVPE) grown over an initial layer deposited by metal organic vapor phase epitaxy on patterned sapphire substrates. Whereas these two differently grown GaN layers are crystallographically homogeneous, they differ largely in their doping level due to high unintentional oxygen uptake in the HVPE layer. This high doping shows up in luminescence spectra, which can be explained by a free-electron recombination band for which an analytical model considering the Burstein-Moss shift, conduction band tailing, and the bandgap renormalization is included. Secondary ion mass spectrometry, Raman spectroscopy, and Hall measurements concordantly determine the electron density to be above 1019cm-3. In addition, the strain state is assessed by Raman spectroscopy and compared to a finite element analysis. [ABSTRACT FROM AUTHOR]