Photo-etching of GaN: Revealing nano-scale non-homogeneities

• The MOCVD- and HVPE-grown GaN layers were etched both photo and orthodically in this study.
• The structures were examined by means of light and electron microscopies.
• The etched nano-pits neither are correlated with the position of the outcrops of dislocations nor on the outcrops of dislocations.
• They result in formation of either protruding etch features or deep, elongated pits.
• Nano-scale non-homogeneities have been revealed in GaN epitaxial layers using multiple etching methods.
• The native point defects such as VGa,ON and the related VGa-ON pairs are the main components of these non-homogeneities.

Nano-scale non-homogeneities in MOCVD- and HVPE-grown gallium nitride were revealed by means of photo-etching in K2S2O8–KOH solution and by chemical etching in hot KOH solution. These non-homogeneities result in formation of protruding etch features and in-depth elongated nano-pits, respectively. High spatial resolution cathodoluminescence evidenced a non-homogeneous distribution of non-radiative recombination centers, which correlates well with photo-etched pattern of protruding etch features. The density of these features is two orders of magnitude higher than this of threading dislocations. A possible association between the non-uniform in nano-scale distribution of native point-type defects, such as VGa, ON and related VGa–ON complexes, and the observed etch features is presented. Existence of such fluctuations may have a large influence on the reliability of nitride-based electronic and optoelectronic devices.