III-V and II-VI Compounds

This article focuses primarily on the properties of the most extensively studied III—V and II—VI compound semiconductors and is presented in five sections (/) a brief summary of the physical (mechanical and electrical) properties of the 2incblende cubic semiconductors (2) a description of the metal organic chemical vapor deposition (MOCVD) process. MOCVD is the preferred technology for the commercial growth of most heteroepitaxial semiconductor material (J) the physics and (4) apphcations of electronic and photonic devices and (5) the fabrication process technology in use to create both electronic and photonic devices and circuits. 

Vessels for Czochralski crystal growth of III-V and II-VI compounds (i.e., gallium arsenide). 

The III-V and II-VI compounds refer to combination of elements that have two, three, five, or six valence electrons. They have semiconductor properties and are all produced by CVD either experimentally or in production. The CVD of these materials is reviewed in Ch. 12. Many of their applications are found in optoelectronics where they are used instead of silicon, since they have excellent optical properties (see Ch. 15). Generally silicon is not a satisfactory optical material, since it emits and absorbs radiation mostly in the range of heat instead of light. 

Most of our current theoretical knowledge centers on group-IV (elemental) semiconductors. While many qualitative results are doubtlessly of general validity, extension to III-V and II-VI compound semiconductors, where technological applications are very promising, is necessary to obtain quantitative answers and broaden our insights. 

A large number of binary AB compounds formed by elements of groups IIIA and VA or IIA and VIA (the so-called III-V and II-VI compounds) also fcrystallize in diamond-like structures. Among the I-VII compounds, copper (I) halides and Agl crystallize in this structure. Unlike in diamond, the bonds in such binary compounds are not entirely covalent because of the difference in electronegativity between the constituent atoms. This can be understood in terms of the fractional ionic character or ionicity of bonds in these crystals. 

Semiconductive elements Si and Ge (Group IVB or 13 in the periodic table) have become very important electronic materials since development of a purification method. The electronic properties of semiconductive elements of high purity can be controlled by the species and concentration of defects and impurity elements. On the other hand, in the case of semiconductive compounds, that is, III-V and II-VI compounds, we have to consider not only control of the purity of constituent elements but also the nonstoichiometry, both of which have much influence on the electronic properties. In this sense, control of the electrical properties of semiconductive compounds is more difficult than that of semiconductive elements. 

Since its invention in 1958 [1], molecular beam epitaxy (MBE) has become well established for the growth of III-V and II-VI compounds as well as for Si and SiGe [2], Among its unique features are ... 

The main native defects in III-V and II-VI compounds are vacancies and atoms in antisites. For instance, the As antisite (Asoa) and the As vacancy (Fas) are residual defects in LEC-grown GaAs crystals [6]. ZnO is a material whose electrical properties are determined by native lattice defect the presence of interstitial Zn correlated with O vacancies (Vo) seems to be responsible for the n-type electrical conductivity of many crystals, but in high-resistivity crystals obtained by hydrothermal growth, the dominant defect is caused by VZn [8],... 

In the following, an attempt to provide the most useful absorption data on centres with donor effective-mass-like properties in semiconductors is made. The group-IV crystals are considered first, and then the III-V and II-VI compounds. 

The splitting discussed here for germanium and in the next subsection for cubic III-V and II-VI compounds concern the ground and excited states of lines G, D, C, and B of the acceptor spectra.. In different references, the... 

Adamantine Group IV elements, III-V and II-VI compounds Covalent, sometimes partly ionic Transparent, high refractive index or opaque Semiconductors except diamond, insoluble Very high melting Very hard, break by cleavage Diamond, carborundum, zinc blende... 

For nc-Si/SiO2 structures of type 1 the PL band maximum shifts from 1.3 to 1.7 eV when d decreases from 4.5 to 1.5 nm the intrinsic PL of nc-Si is commonly explained by the radiative recombination of excitons confined in nc-Si, while the size dependent spectral shift is attributed to the quantum confinement effect [21]. A considerable width of the PL band can be explained by nc-Si size distribution [21] as well as by phonon-assisted electron-hole recombination [22]. The external quantum yield of the exciton PL was found to reach -1 % for the samples with d = 3 - 4 nm at room temperature [18]. The lower quantum yield of the nc-Si/SiO2 structure in comparison with that observed for single Si quantum dots [22] and for III-V and II-VI compounds [22] can be explained by lower probability of the optical transitions, which are still indirect in nc-Si [21], as well as by the exciton energy migration in the assembly of closely packed nc-Si [18]. 

Mujica A, Rubio A, Munoz A, Needs RJ (2003) High-pressure phases of group IV, III-V, and II-VI compounds. Rev Modem Phys 75 863-912... 

Due to the relatively poor thermal conductivity and low yield stresses of III-V and II-VI compounds, as compared with Ge and Si, it is not possible to reduce the thermal stresses to a suffidently low level to avoid dislocation multiplication. However, recent developments in vertical gradient freeze techniques have produced a marked reduction ofdislocation density in undoped GaAsand InP. InVGF growth the establishment of a uniaxial heat flow has led to minimum dislocation densities below 10 cm and 10 cm in 4-inch undoped and Si-doped GaAs crystals, respectively. 

Quantitative information about dimer vibration and e-p interaction can be elucidated by matching predictions to the measured shape and size dependence of Raman and photoemission/absorption spectra of Si and other III-V and II-VI compounds. The CN imperfection of different orders unifies the phase stability of ferromagnetic, ferroelectric, and superconductive nanosolids. In conjunction with the previous bond-band-barrier correlation mechanism, the present approach allows us to distinguish the extent of oxidation and contribution of surface passivation to the dielectric susceptibility of porous silicon [16]. 

Sphalerite or zinc blende is the chief ore of ZnS. ZnS as well as many of the III-V and II-VI compound semiconductors such as GaAs form a diamond-like stmeture with one type of atom on the fee lattice sites and the other type of atom on every other tetrahedral site. The space group is F43wx (the d-glide plane symmetry in diamond is lost by the fact that different atoms occupy the interstitial sites). Since there are four atoms on the lattice points of the fee unit cell, the stoichiometry is maintained if half of the eight tetrahedral sites are occupied by the second atom. For these systems, the double stacking described above would have different atoms in doubled layers, i.e., A(Zn) A (S) B(Zn) B (S) C(Zn) C (S), etc. This type of structure is the same as shown in Figure 5.9 if the black spots are... 

A significant body of work from both experimental and theoretical points of view has been done on grain boundaries in covalently bonded III-V and II-VI compounds, the structure and the associated electronic structures of which strongly affect electronic properties of devices. Specific grain-boundary structures have been observed by the HRTEM technique, and also a number of sophisticated methods of calculation have been provided to determine structural and electronic properties. However, a detailed description is beyond the scope of this chapter. 

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