The electronic charge densities in semiconducting layer and chain structures

Abstract

Abstract-From calculations of the pseudo-wavefunctions the charge densities of the valence electrons , in the semiconducting crystals SnSe,, Pbl,, GaSe, Se and Te have been determined. The results are compared with the valence bond description of semiconductors which can thus be confirmed and refined. Insight is gained into the ::J,CCommodation in the valence bands of the excess s-electrons in Pbl, and GaSe. For Te the transformation from the trigonal to the simple cubic modification has been simulated on the computer. The changes of the charge densities occuring in this semiconductor-to-metal transition are discussed.

Elementary energy bands concept, band structure, and peculiarities of bonding in β-InSe crystal

“…In particular, the existence of states for which anomalous dispersion of the branches of band structure of the β‐InSe crystal near the top of valence band was confirmed in Ref. 15. A similar anomaly in the band structure of another polytype (γ‐InSe) was also found in Refs.…”

Non‐standard anisotropy of the energy spectrum of a layered TlGaSe2 crystal

“…This ratio for the electron and hole effective mass obtained in the parabolic approximation for the directions ${\Gamma} {-} Q_{1} $ and ${\Gamma} {-} F_{1} $ is abnormal, since one should expect that $(m_{e,h}^{*} /m_{0} )_{{\Gamma} {-} N} $ should be larger than $(m_{e,h}^{*} /m_{0} )_{{\Gamma} {-} Q_{1} ,{\Gamma} {-} F_{1} } $ . A similar situation took place in the case of other indium and gallium selenides 2, 12, 13, 26. The abnormal dispersion in the direction $Q_{1} {-} {\Gamma} {-} F_{1} $ is caused in our opinion, also by a low‐energy non‐parabolicity of the dispersion relation $E({\bf k})$ for the conduction band.…”

“…However, this belief for a series of complicated layered crystals is not correct. Mooser et al, as far as the authors know, have reported about this situation for the first time, when they observed an abnormal dispersion of bands in the band structure of GaSe, near the top of the valence band 2. A similar dispersion was obtained also for β ‐InSe 26.…”

“…In consequence, there exist an extensive review concerning electronic properties and phase transitions of low‐dimensional thallium contained semiconductors, including the investigated below TlGaSe 2 crystal 1. The TlGaSe 2 crystal exhibits a sequence of low‐temperature phase transitions at atmospheric pressure and contains some structural units of the layered GaSe crystal for which the abnormal dispersion of branches of the electronic spectrum has been observed for the first time 2. Since a number of physical properties of a crystal is conditioned by its band structure, it requires a precise calculations, explanation of topology and description of energy states symmetry.…”

Electronic and vibrational spectra of III-VI layered semiconductors

“…Within the layers the bonding is of an ionic-covalent character, while between layers the interaction is predominantly of the van der Waals type, with a small Coulombic admixture. 13 ' 14 The structure of the layers is the same in GaS, GaSe, and InSe. The anions and cations are arranged in planes perpendicular to the C axis in the sequence (for GaS, say) S-Ga-Ga-S.…”