Polytype/polytypism wurtzite-zinc blende

The structure of both the SiC and ZnS polytypes can be illustrated with reference to the crystalline forms of ZnS. Zinc sulphide crystallises in either of two structures, one of which is cubic and given the mineral name zinc blende (sphalerite) while the other is hexagonal and given the mineral name wurtzite. The relationship... 

Silicon carbide, carborundum, also crystallises in two forms, of which /(-SiC has the cubic zinc blende (sphalerite) structure (Figure 8.8a). When viewed along the cube face-diagonal [110] direction, the layers of both silicon and carbon are packed in the cubic closest packing arrangement. .. aAbBcCaAbBcC. .., where the uppercase and lowercase letters stand for layers of Si and C. The other form of silicon carbide, a-SiC, is a collective name for the various silicon carbide polytypes, which consist of complex arrangements of zinc blende and wurtzite slabs. Some of these are known by names such as carborundum I, carborundum II, carborundum III, and so on. One of the simplest structures is that of carbo-... 

The layer sequences can repeat themselves in the cycles ABC, ABC. .. (zinc blende, type 3C) or AB, AB. .. (wurtzite, type 2H), according to cubic or hexagonal close packing. In addition, numerous others stack sequences are formed in the case of silicon carbide, resulting in many similar polytypes. 

Yeh, C.-Y, Lu,Z. W, Froyen, S., Zunger, A. (1992b). Zinc-blende-wurtzite polytypism in semiconductors. Physical Review B, 46,10086-10097. 

The BSFs in GaN do not introduce localized states in the band gap, but can be considered as a thin zinc-blend (ZB) layer embedded in the wurtzite (W) matrix. The theory predicts that this polytypic QW has a type 11 band alignment with a conduction band offset of about 270 meV [55]. The D1 emission can be described as a recombination of electrons confined in the ZB region with holes residing in the W barrier. At low temperatures, the holes are expected to be localized in a triangular potential notch formed in the barrier because of the discontinuity of the spontaneous polarization across the ZB-W interface [55]. Thus, the emission occurs between separately localized but closely spaced electrons and holes. At higher temperatures, the holes become delocalized and the emission is attributed to a recombination between electrons still localized in ZB QW and holes are attracted to them by Coulomb interaction. This... 

Figure 1.6 Stick-and-ball stacking model of crystals with (a, both top and bottom) 2H wurtzitic and (b, both top and bottom) 3C zinc blende polytypes. The bonds in an A-plane (112 0) are indicated with heavier lines to accentuate the stacking sequence. The figures on...

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