A technique, based upon photo-electrochemical wet-etching, was described which permitted the accurate evaluation of dislocation densities in n-type films. The etching process used dilute aqueous KOH solution and Hg arc-lamp illumination to produce etched nitride whiskers by selectively etching away the material around threading dislocations. The etched whiskers, each of which corresponded to a single threading dislocation, could be effectively imaged by means of plan-view scanning electron microscopy. The dislocation distribution and density were then easily observable over very large sample areas. Transmission electron microscopy and atomic force microscopy of the samples confirmed the accuracy of the dislocation densities which were deduced by wet etching.

Rapid Evaluation of Dislocation Densities in n-Type GaN Films using Photoenhanced Wet Etching. C.Youtsey, L.T.Romano, R.J.Molnar, I.Adesida: Applied Physics Letters, 1999, 74[23], 3537-9