The band gaps, band structure, and excited‐state (exciton) energies of CdS, GaAs, and GaP semiconductor clusters are calculated using pseudopotentials. In addition, the sensitivity of the exciton energies to the size, shape, crystal structure, and lattice constant of the unit cell are investigated. The calculated exciton energies of CdS clusters are in excellent agreement with experiment over a wide range of cluster sizes. Also, the exciton states of small CdS clusters are sensitive to whether their crystal structure is zinc blende or hexagonal. Such a sensitivity is absent in large CdS clusters. Furthermore, small GaAs clusters are shown to exhibit anomalous redshift of their absorption spectra, in sharp contrast to CdS and large GaAs clusters whose spectra always shift to blue with decreasing cluster size. Finally, the lowest‐energy non‐Franck–Condon transition in GaP clusters always shifts to blue with decreasing cluster size, whereas the higher‐energy Franck–Condon transition in small clusters exhibits the anomalous redshift. These novel findings reveal that (1) the optical spectroscopy of semiconductor clusters is strongly material and crystal structure dependent; (2) the spectroscopy of small clusters is dramatically different from those of large clusters and bulk; and (3) these effects cannot be explained, even qualitatively, using the effective‐mass approximation.

Quantum confinement effects in semiconductor clusters

Publisher Summary The chapter presents a study on the relationship between structure, vibrational dispersion relations, and band structure for chalcopyrite and related compounds. The essential step in this procedure is the “folding” of the dispersion relations [ ω (k) or E (k)] for the simplest structure into the smaller Brillouin zone of the more complicated one. In one-dimensional models, such folding is trivial enough and is discussed in relation to the nearly free electron approximation, Peierls instability, and so on. In three dimensions, it is more complex and therefore merits the detailed and concentrated description that is presented in this chapter. In addition to the chalcopyrites, the chapter includes certain quaternary and “defect” or “vacancy” compounds, such as HgIn 2 Te 4 . The vacancy compounds may be considered to have tetrahedral structures with a sublattice of unfilled sites. In this case, it is questionable whether the compound is to be regarded as derived from its parent structure by a small perturbation, as is often assumed for chalcopyrites. Compounds that have tetrahedrally coordinated structures generally have an average number of four valance electrons per atom. This is the Grimm–Sommerfeld rule.

Beyond the Binaries—The Chalcopyrite and Related Semiconducting Compounds

Pressure coefficients of band gaps in semiconductors

Structure/property regulation is widely investigated for providing theoretical foundations and guidance for designing microwave dielectric ceramics. P–V–L bond theory targets the provision of detailed structural parameters of crystals and fundamental chemical bond characteristics, such as bond ionicity, bond covalency and bond susceptibility. In this review, the concept of P–V–L bond theory, the binary bonding formula theory of complex polycrystalline and the usage of P–V–L bond theory regarding the structural effects on dielectric properties in various crystal structures are introduced. And the bond traits provided via P–V–L bond theory in several ion-doping modification systems are generalized with structural evolution and dielectric properties. Furthermore, conjectures about the development and application directions of P–V–L bond theory in the study of structure/properties of microwave dielectric ceramics are put forward.

Usage of P–V–L bond theory in studying the structural/property regulation of microwave dielectric ceramics: a review

Dependence of the indirect energy gap of silicon on hydrostatic pressure

Reflectivity spectra of the chalcopyrite ternary compound ZnGe${\mathrm{P}}_{2}$ are studied experimentally and theoretically. The measurements of the reflectivity in both the complete parallel and perpendicular polarizations are made at 5\ifmmode^\circ\else\textdegree\fi{}K. A full zone energy-band structure, the reflectivity and imaginary part of the frequency-dependent dielectric function are calculated using the empirical pseudopotential method. Comparison is made with the measured reflectivity and modulated reflectivity and prominent features in the experimental spectra are identified and associated with interband transitions. In addition, spin-orbit interactions are included at a few points of the Brillouin zone.

/pdf/calculated-and-measured-reflectivity-of-zngep-sub-2-1zm2b9xdl4.pdf

Calculated and measured reflectivity of ZnGeP/sub 2/

Modulated-reflectivity measurements of InP and GaP at 5, 77, and 300 \ifmmode^\circ\else\textdegree\fi{}K are compared with empirical-pseudopotential calculations of the electronic band structure, the imaginary part of the frequency-dependent dielectric function, and the derivative of the reflectivity.

/pdf/wavelength-modulation-spectra-and-band-structures-of-inp-and-sx9l28zpgp.pdf

Wavelength-Modulation Spectra and Band Structures of InP and GaP

Measured x-ray-photoemission spectra for ZnGeP/sub 2/ and CdSnAs/sub 2/ are presented along with density-of-states N(E) and charge-density calculations for ZnGeP/sub 2/. Analysis of the density-of-states spectra illustrates the relation between N(E) structure and bonding properties, allowing spectral peaks to be assigned to specific bonds.

/pdf/electronic-density-of-states-and-bonding-in-chalcopyrite-2dsjjbt58y.pdf

Electronic density of states and bonding in chalcopyrite-type semiconductors

https://escholarship.org/content/qt1qg842md/qt1qg842md.pdf?t=p2atu7

Calculated band structures, optical constants and electronic charge densities for InAs and InSb

https://escholarship.org/content/qt00f576s5/qt00f576s5.pdf?t=p0uvt5

Carmen Varea de Alvarez

Papers

Calculated and measured reflectivity of ZnGeP/sub 2/

Wavelength-Modulation Spectra and Band Structures of InP and GaP

Electronic density of states and bonding in chalcopyrite-type semiconductors

Calculated band structures, optical constants and electronic charge densities for InAs and InSb

Pressure coefficients for band gaps in silicon