Zinc-blende–wurtzite polytypism in semiconductors

Abstract

The zinc-blende (ZB) and wurtzite (W) structures are the most common crystal forms of binary octet semiconductors. In this work we have developed a simple scaling that systematizes the T=O energy difference bE~z a between W and ZB for all simple binary semiconductors. We have first calculated the energy difference hE "za( AB) for A1N, GaN, InN, A1P, A1As, GaP, GaAs, ZnS, ZnSe, ZnTe, CdS, C, and Si using a numerically precise implementation of the first-principles local-density formalism (LDF), including structural relaxations. We then find a linear scaling between AE~"za(AB) and an atomistic orbital-radii coordinate R( A, B) that depends only on the properties of the free atoms A and B making up the binary compound AB. Unlike classical structural coordinates (electronegativity, atomic sizes, electron count), R is an orbital-dependent quantity; it is calculated from atomic pseudopotentials.The good linear fit found between hE za and R {rms error of -3 meV/atom) permits predictions of the W -ZB energy difference for many more AB compounds than the 13 used in establishing this fit. We use this model to identify chemical trends in hE~z a in the IV-IV, III-V, II-VI, and I-VII octet compounds as either the anion or the cation are varied. W'e further find that the ground state of Mg Te is the NiAs structure and that CdSe and HgSe are stable in the ZB form. These compounds were previously thought to be stable in the W structures.

Why Does Wurtzite Form in Nanowires of III-V Zinc Blende Semiconductors?

“…Calculations give the difference δw in cohesive energy between ZB and WZ bulk GaAs as about 24 meV per III-V pair at zero pressure [7]. It has been argued that this favoring of the ZB form might be offset in NWs of small diameter by the large relative contribution to the total energy of either the lateral facets [12] or the vertical edges separating the latter [13] (provided the specific energies of these features are less for WZ than for ZB).…”

“…3). In the former case (hereafter 'ZB position') the GaAs 4 tetrahedra have the same orientation if the Ga atom belongs either to nucleus or to previous ML whereas tetrahedra and nucleus are rotated by an odd multiple of π/3 in the latter case ('WZ position') [7]. ZB and WZ sequences require the nucleation of each ML in, respectively, ZB and WZ position with respect to the previous ML.…”

“…We consider III-V compounds which, under bulk form, adopt the cubic zinc-blende (ZB) crystal structure [7] (although some non-ZB high-pressure phases [8] may be metastable at atmospheric pressure [9]), leaving aside nitrogen-based NWs. We discuss the usual case of NWs grown on a [111]B (As-terminated) face of the ZB substrate.…”

“…Metal catalyst nanoparticles deposited on the substrate before growth define the wire diameter. According to the vapor-liquidsolid (VLS) growth mechanism, the atoms are fed from the vapor phase to the solid wire through this particle (or droplet), which remains liquid during growth [6].We consider III-V compounds which, under bulk form, adopt the cubic zinc-blende (ZB) crystal structure [7] (although some non-ZB high-pressure phases [8] may be metastable at atmospheric pressure [9]), leaving aside nitrogen-based NWs. We discuss the usual case of NWs grown on a [111]B (As-terminated) face of the ZB substrate.…”

Mechanically controlling the reversible phase transformation from zinc blende to wurtzite in AlN

“…Wurtzite (wz) and zinc blende (zb) are two common phases in these materials [4,5] and the crystal structure has been proven to be critical in determining the corresponding functional performance [2,6]. For example, by changing the crystal structure of GaP semiconductors from zinc blende to wurtzite, the band gap changes from indirect to direct, resulting in a significant enhancement of the efficiency of white light-emitting diodes [6].…”