Boiling KOH etching behavior of GaN buffer and epitaxial layers on sapphire substrate - Effects of substrate-surface nitridation and carrier gas

Abstract

Boiling KOH etching behavior of MOVPE GaN layer has been studied to understand the effects of substrate nitridation and carrier gas on its polarity. Relationships of the polarity between buffer and epitaxial layers are also studied. When H2 carrier gas is used, an epitaxial layer grown on a nitrided substrate shows a very low etching rate, i.e. Ga polarity, while the N polarity is dominant for that grown on a non-nitrided substrate. In both cases, the dominant polarity in the buffer and the epitaxial layer coincides each other. Buffer layers grown with N2 carrier gas grown on a nitrided substrate show a high dissolution rate as if N-polarity domains are dominant, although Ga-polarity epitaxial layers are grown on those buffer layers. This means that buffer layers grown with N2 carrier are of poor quality (defective). © 2002 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1610.