Mg doping concentration influenced by the polarity of the GaN layer in InGaN/GaN superlattice structures

摘要

The polarity of InGaN/GaN superlattice structures grown on c-plane sapphires by metal-organic chemical vapor deposition (MOCVD) comprised of an GaN buffer layer doped with different impurities is studied. Photoluminescence (PL) was employed to determined the emitting characteristics of the samples. Secondary ion mass spectroscopy was used to examine the concentration of the constituents along the growth direction. Convergent beam electron diffraction (CBED) was used to determine the symmetry of the crystal. In addition, the polarity of the samples was also demonstrated by a simpler method of chemical etching in a KOH aqueous solution compared with the analysis of the CBED pattern. Our central results show that the variety of dopants in the GaN buffer layer would determine the polarity of the top GaN layer, which then influence the emitting performance of the InGaN/GaN superlattices.