Morphology, interface polarity and branching of electrochemically etched pores in InP

Abstract

AbstractThe 3‐dimensional morphology of individual pores grown in InP(001) by electrochemical etching, their interface polarities and their branching behavior have been investigated by transmission electron microscopy (TEM) in various crystal lattice projections and by convergent‐beam electron diffraction (CBED). Pores start to grow irregularly shaped with preferential orientation perpendicular to the surface. Following this nucleation layer long straight pores with triangular cross‐section grow deep into the crystal along inclined 〈111〉B directions. Along the pore axis the pore diameter oscillates. The morphology of the pore tips can be described approximately by a chain of interconnected tetrahedrons bounded by {111}A‐facets. Some pores show additional {001} facets at the transition regions between the tetrahedrons. With increasing distance from the pore tips the mean pore diameters increase and the pores approach the shape of open prismatic channels with channel walls that are bounded, on the average, by {112}‐planes. Self‐assembling pore branching in all four 〈111〉B crystal directions leads to 3‐dimensional pore arrangements which are of considerable interest for the fabrication of photonic crystals. – We discuss the observed pore morphologies within the framework of a model that describes the pore formation as an interplay of dissolution and surface passivation with the surface passivation being affected by the crystal polarity of the material. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)