A first principles study of the lattice stability of diamond-structure semiconductors under intense laser irradiation

Abstract

Using density-functional linear-response theory, we calculated the phonon dispersion curves for the diamond structural elemental semiconductors of Ge, C and zinc-blende structure semiconductors of GaAs, InSb at different electronic temperatures. We found that the transverse-acoustic phonon frequencies of C and Ge become imaginary as the electron temperature is elevated, which means the lattices of C and Ge become unstable under intense laser irradiation. These results are very similar with previous theoretical and experimental results for Si. For GaAs and InSb, not only can be obtained the similar results for their transverse-acoustic modes, but also their LO-TO splitting gradually decreases as the electronic temperature is increased. It means that the electronic excitation weakens the strength of the ionicity of ionic crystal under intense laser irradiation.

Ab initio study of lattice instabilities of zinc chalcogenides ZnX (X=O, S, Se, Te) induced by ultrafast intense laser irradiation

“…42 Consequently, the dipoles induce the electric field and influence the LO-TO splitting degree (δω) which assesses the ionic strength of ionic crystals at Γ point. 8,11 In Table II, he phonon frequencies at the high symmetry Γ point for ZnX at T e = 0 eV are consistent with the previous calculated values by groups. 8,45 The calculated TO and LO phonon frequencies at Γ point are 385 cm -1 and 509 cm -1 for ZnO, 264 cm -1 and 330 cm -1 for ZnS, 195 cm -1 and 235 cm -1 for ZnSe, 177 cm -1 and 202 cm -1 for ZnTe, respectively, which are close to the experimental values of 276 cm -1 (TO) for ZnS, 47 213 cm -1 (TO) for ZnSe, 26,46 177 cm -1 (TO) for ZnTe.…”

“…Consequently, laser-induced ultrafast phase transition in semiconductors is the non-thermal phase transition that is different from the conventional thermal transition. 11 That the laser-semiconductor interaction lead to the athermal transition has been confirmed. 12,13 Even though considerable experimental and theoretical work on ZnX, there appear to be limited theoretical studies on the excitation effect of ultrafast intense laser irradiation on ZnX in the literature.…”

“…Additionally, current activities for ultrafast intense laser pulse interaction with semiconductors have been paid significant attention. [9][10][11][12][13] To begin with, the effect of intense laser irradiation on the lattice stability of β-SiC was studied by ab initio calculation within the density functional perturbation theory (DFPT) by Shen et al 9 It is also shown that electronic excitation in silicon can induce lattice instabilities as exhibited by transverse-acoustic (TA) phonon modes with imaginary frequencies. 10 As the interaction of semiconductors with ultrafast intense laser, the electrons in the semiconductors are excited and then heated to a high temperature (thousands of Kelvins) within tens of femtoseconds.…”

Ab initio investigation of photoinduced non-thermal phase transition in β -cristobalite

“…The critical electronic temperature of the complete transverse acoustic branch becoming imaginary for fcc β -cristobalite is between 1.5 eV and 2.0 eV. Similar studies [16,27,28] have been conducted for semiconductors Si, C, Ge, InSb, and GaAs, and similar results have been obtained for them.…”

“…Their studies showed that extreme carrier densities destabilize the crystal structure and lead to non-thermal melting of InSb. In addition, theoretical investigations have found that the transverse acoustic mode of several semiconductors, [14][15][16] such as C, Si, Ge, GaAs, and InSb, becomes unstable if about more than 9% of the valence electrons are excited into the conduction band. But neither experiments nor calculations are available to find out whether cristobalite undergoes such a non-thermal melting transition as semiconductors C, Si, Ge, GaAs, and InSb [14][15][16][17] at the excitation levels of > 9% of the valence electrons.…”