Cubic Semiconductors

High-resolution measurements of the discrete spectrum of donors in high-purity GaAs and InP have been performed by PTIS and in most cases, the spectra have been obtained under a magnetic field to reduce the spatial amplitude of the wave function, in order to limit the interaction between the electrons bound to neighbouring donors. With the application of a magnetic field, the FWHMs of the individual lines are drastically reduced and a comparison with the zero-field spectrum can be made in Fig. 6.41a, b. 

The possibility of two-photon absorption (TPA) due to non-linear effects has been mentioned in Sect. 4.1. The magnetic-field-tuned LHeT absorption by n-type GaAs of a laser line at 20.2 cm-1 (2.50 meV) has been reported by [28] for B = 1.15 T and attributed to a two-photon Is — 2s transition at 40.4cm 1 (5.00meV). The fact that the initial and final states of this transition have the same parity can be explained by assuming an odd-parity 

The existence of metastable quasi-hydrogenic donor (QHD) states associated with Landau levels with N 0 for large values of the magnetic field has been mentioned in Sect. 5.2.3. The absorption of a large number of such states has been observed on GaAs for relatively high doping levels, as shown in Fig. 6.43. 

The situation for InSb is somewhat different, the reason being the small electron effective mass and large dielectric constant, which result in a rather large effective Bohr radius pm for n = 2 state) and a small value 

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Aspnes D E 1985 Above-bandgap optical anisotropies in cubic semiconductors a visible-near ultraviolet probe of surfaces J. Vao. Sc/. Teohnoi. B 3 1498-506... 

Huang Ming-Zhu and Ching WY 1993 Caicuiation of opticai excitations in cubic semiconductors, i. Eiectronic structure and iinear response Phys. Rev. B 47 9449-63... 

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. 

Table 3.6. Experimentally-determined effective masses (in units of me) at k = 0 extrema and VB Luttinger parameters for some direct-band-gap cubic semiconductors...

In the classical electron transport model in metals or semiconductors, for a material with a free electron concentration n and an average electron scattering time (also called relaxation time) r, the DC conductivity is Oo = ne2r/to. In this classical expression, m (m or m ) is the conductivity effective mass, which is an average mass different from the DoS effective mass (see for instance [4]. In cubic semiconductors with degenerate CB extrema, the conductivity effective mass for electrons is ... 

The symmetry of an isolated atom is that of the full rotation group R+ (3), whose irreducible representations (IRs) are D where j is an integer or half an odd integer. An application of the fundamental matrix element theorem [22] tells that the matrix element (5.1) is non-zero only if the IR DW of Wi is included in the direct product x of the IRs of ra and < f. The components of the electric dipole transform like the components of a polar vector, under the IR l)(V) of R+(3). Thus, when the initial and final atomic states are characterized by angular momenta Ji and J2, respectively, the electric dipole matrix element (5.1) is non-zero only if D(Jl) is contained in Dx D(j 2 ) = D(J2+1) + T)(J2) + )(J2-i) for j2 > 1 This condition is met for = J2 + 1, J2, or J2 — 1. However, it can be seen that a transition between two states with the same value of J is allowed only for J 0 as DW x D= D( D(°) is the unit IR of R+(3)). For a hydrogen-like centre, when an atomic state is defined by an orbital quantum number , this can be reduced to the Laporte selection rule A = 1. This is of course formal, as it will be shown that an impurity state is the weighted sum of different atomic-like states with different values of but with the same parity P = ( —1) These states are represented by an atomic spectroscopy notation, with lower case letters for the values of (0, 1, 2, 3, 4, 5, etc. correspond to s, p, d, f, g, h, etc.). The impurity states with P = 1 and -1 are called even- and odd-parity states, respectively. For the one-valley EM donor states, this quasi-atomic selection rule determines that the parity-allowed transitions from Is states are towards np (n > 2), n/ (n > 4), nh (n > 6), or nj (n > 8) states. For the acceptor states in cubic semiconductors, the even- and odd-parity states labelled by the double IRs T of Oh or Td are indexed by + or respectively, and the parity-allowed transition take place between Ti+ and... 

Table 5.14. Values of the parameters S and p determining the importance of the cubic contribution over the spherical term for different cubic semiconductors deduced from Tables 3.4 and 3.6...

The OSs for shallow acceptor transitions between ground state (0) with degeneracy go and final state (/) in cubic semiconductor can be expressed as ... 

Table 8.23. Values of the (/-factors of the ground and first excited states (g J) (Tr )) of different acceptors in compound cubic semiconductors. For some acceptors, the g[J Oh) values are given in parentheses...

Mercury selenide is a zero-gap material (semimetal). The lowest conduction band minimum and the top of the valence band are degenerate at the center of the Brillouin zone (Fg). The F level, which for most cubic semiconductors is the conduction band minimum and has an energy larger than that of the Fg state, is found to be below the Fg state in HgSe ( negativ energy gap , inverted band structure). 

Bagdavadze, V. N., and Berozashvili, Yu. N., Electrooptic effect in noncentrosym-metric cubic semiconductor crystals with allowance for spatial dispersion, Sov. Phys. Semiconductors, 12, 1115 (1978). 

Bell, M. I., Electro-optic coefficients of cubic semiconductors, in 11th International Conference on the Physics of Semiconductors—Proceedings, Vol. 2, 1972, p. 845. 

Results obtained on other semiconductors are finally mentioned for discussing whether a plastic deformation regime controlled by perfect dislocations is a generic property of diamond-cubic semiconductors. 

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