Studies for the structural stability of zinc blende (ZB) and wurtzite (WZ) structured A^NB^<8-N> compounds are reviewed from the viewpoint of computational science. Relative stability between ZB and WZ is discussed in terms of energy difference between ZB and WZ obtained by ab initio calculations, ionicity, atomic orbital radii, interlayer and interatomic interactions. Furthermore, the origin of the structural stability of ZB and WZ is investigated on the basis of these approaches, where interactions beyond the second nearest neighbor atoms incorporating bond characteristics are crucial for interpreting the relative stability between them.

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Metalorganic vapor phase epitaxy of zincblende GaN and molecular beam epitaxy of zincblende InN are presented. High quality zincblende GaN can be grown under the condition of low V/III ratio and high growth temperature. Since wurtzite GaN tends to grow on {111} facets of zincblende GaN, it is important for preventing the mixing of wurtzite to maintain the (001) surface of zinblende during growth. High purity and high quality zincblende InN also can be grown under the condition of low V/III ratio and high growth temperature. Thus, low V/III ratio, high growth temperature and flat surface are keys to epitaxial growth of high purity and high quality zincblende nitride semi-conductors.

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Theoretical approach for the epitaxial growth of GaN, ZnO and related compound semiconductors having the wurtzite structure is introduced. In this review, we introduce the results for GaN (0001), ZnO (0001), GaN (1120), ZnO (1120), GaN (1010), ZnO (1010), GaN/sapphire (0001), AlN/sapphire (0001), InN/sapphire (0001), ZnO/sapphire (0001), GaN/SiC (0001), ZnO/SiC (0001) and ZnO/SiC (0001). In the theoretical approach, the first principles density functional theory calculation has been used to obtain the potential energy surface for the supplied adatom during the epitaxy. The kinetic Monte Carlo simulation has been also used for the confirmation of the anisotropic morphology formation.

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We investigated the growth conditions of cubic GaN (c-GaN) by ab initio based approach which incorporates free energy of vapor phase. It is known that a c-GaN is a meta-stable phase and wurtzite GaN (h-GaN), which is a stable phase of GaN, is easily incorporated in the c-GaN crystal during growth. h-GaN is formed in the area grown on {111} facet plane. In the present study, therefore, we studied the growth conditions of {111} facet formation in order to clarify the conditions of h-GaN incorporation. The results suggest that we can suppress the {111} facet formation, i.e., h-GaN mixing, by controlling the growth conditions such as temperature and gallium beam equivalent pressure.

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We have studied the wurtzite (W)-zincblende (ZB) polytypism in ZnSe films grown the GaAs (111) A-(2×2) substrate. While the stable structure of bulk ZnSe is ZB, W-structured ZnSe is formed near the interface on the ZB-structured GaAs (111) A substrate. Our first-principles calculations have revealed that the charge state at the ZnSe/GaAs (111) A interface plays a key role in the formation of W-ZnSe. In addition, we show that the structural quality of W-ZnSe is significantly improved using a cracked Se-source, while ZB-ZnSe is grown using a vicinal GaAs (111) A substrate.

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GaAs and InAs nanowires were selectively grown by using metal-organic vapor-phase epitaxy. The nanowires were as thin as several tens to several hundreds nanometers and as long as several micronmeters. Scanning electron microscope observations showed that the growth direction of nanowires was parallel to the <111> B crystallographic orientation. It was found by a transmission electron microscopy analysis that the crystal structure of the GaAs nanowire was zincblende with rotational twins around the <111> axis. For the GaAs nanowires, the density of twins along the <111> direction increased as the nanowire diameter decreased. The growth mechanism was understood based upon a model that the GaAs nanowire was composed of stacked thin-layers with interfaces containing rotational twins.

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Recently, one-dimensional semiconductor nanostructures called "nanowires" are attracting much interest due to their applications for future nano-devices. It is, however, reported that nanowires fabricated using compound semiconductor materials include wurtzite segments such as rotational twins. In this work, we focus on the fact that the number of atoms constituting the nanowire facets is large compared to the total number of nanowire atoms. Based on our computational approach using system energy calculations, we systematically investigate the relative stability between zinc blende-wurtzite structures in compound semiconductor nanowires, and discuss the incorporation of wurtzite segments upon the zinc blende structure during nanowire growth.

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