Characterization of GaN single crystals by defect‐selective etching

Abstract

In this communication it is shown that both “orthodox” etching in molten KOH–NaOH eutectic (E etch and its modification) and photo-etching in aqueous KOH solution (PEC method) permit quick assessment of density, distribution and, after appropriate calibration, type of defects in GaN single crystals and epitaxial layers. Characteristic features of both etching methods are briefly discussed. It is shown that dislocations and micro-defects can be revealed in the form of etch pits (in “orthodox” E etch) and as etch hillocks (PEC method) on both Ga- and N-polar surfaces. The reliability of both methods has been confirmed by direct TEM calibration and by using indentation method. Very low dislocation density (EPD ≤ 2 × 102 cm–2) in the undoped GaN single crystals and MOCVD-grown epitaxial layers has been confirmed by this study.