Determination of the crystallographic polarity of {111}‐InP crystals by the kossel technique and chemical etching

Abstract

InP and Ga,In, -.P,As, -y epitaxial layers matched to InP are of interest for the production of light emitting devices. In this connection a simple etching method is desirable to identify the polarity of { 1 1 11 crystals. l h e (1 11) and (TTT) surfaces of an InP crvstal correspond to In(A) and P(B) surfaces, respectively. Most polishing etches for 111-V semiconductors develop flat mirror-like surfaces on the (TIT) faces and reveal dislocation etch pits on the In order to confirm this determination we performed a Kossel experiment. As IS known iom the Kossel effect there is no analogy to Friedel's law and hence the polar reflections (hkl) and (fin) show different fine structures (v. LAUE). Thus the polar surfaces of different compound semiconductors have been identified using proton and/or electron excitation of the characteristic X-rays (BRUMMER et al.; ULLRICH et al., GEIST et al. 1974, 1977, 1982. Figure 2 schematically gives the experimental assembly for recording proton beam induced Kossel patterns. The collimated 1 MeV proton beam was directed successively to both sides of the InP slice in order to produce PK, { 11 l} reflections appearing in the geometry of the symmetrical Bragg and asymmetrical Laue case (referring to the vertex of the line). The energetic protons generate X-radiation of the P-lattice atoms with high efficiency. If the Bragg condition is fulfilled for this radiation, Kossel interferences can be formed in-