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 K OH, is presented. A detailed analysis of the etching rate dependence with t emperature and concentration is described. This etching has been used for t he fabrication of high optical quality pyramidal nanostructures in wurtzite N-face GaN grown on AlN-buffered Si(111) substrates by molecular beam epit axy. These nanostructures have been studied by high-resolution transmission and scanning electron microscopy and their optical quality has been analys ed by low-temperature photoluminescence (PL) measurements. The pyramids are parallel to the basal plane and limited by {11 (2) over bar1} planes and i ts presence improves the overall PL response of the sample. The relationshi p between the polarity of GaN and the characteristics of the AlN buffer has also been analysed.