Wet etching of GaN grown by molecular beam epitaxy on Si(111)

A wet etching method for GaN and AlxGa1-xN, based on aqueous solutions of KOH, is presented. A detailed analysis of the etching rate dependence with temperature and concentration is described. This etching has been used for the fabrication of high optical quality pyramidal nanostructures in wurtzite N-face GaN grown on AlN-buffered Si(111) substrates by molecular beam epitaxy. These nanostructures have been studied by high-resolution transmission and scanning electron microscopy and their optical quality has been analysed by low-temperature photoluminescence (PL) measurements. The pyramids are parallel to the basal plane and limited by {11 (2) over bar1} planes and its presence improves the overall PL response of the sample. The relationship between the polarity of GaN and the characteristics of the AlN buffer has also been analysed.