Theory of free‐carrier absorption in n‐PbSe

Abstract

Theory of Free-Carrier Absorption in n-PbSe l) J. S Z Y M A~S K IFree-carrier absorption is calculated for n-type PbSe using the model of a nonparabolic, nonspherical, and multivalley conduction band. New scattering mechanisms of the electron in PbSe-like structure (two-band deformation potential for optical phonons and twooptical-phonon deformation potential) are considered in order t o explain the recent experimental data on n-PbSe.L'absorption par les porteurs libres est calcul6e pour n-PbSe utilisant le modele de la bande de conduction Zt plusieurs vallbes nonspheriques et nonparaboliques. Ppur expliquer les exphriences pour n-PbSe on considhe des nouveaux processus de diffusion des porteurs libres diis aux interactions nonpolaires des 6lectrons avec les phonons optiques. l) This work was supported by the Institute of Physics of the Polish Academy of Sciences. a) Of course, t(w) does not depend, by definition, on the electron energy and exists even if the relaxation time approximation for Boltzmann equation does not hold.

Electron Scattering Interaction and Elementary Excitations in Lead Chalcogenides

“…8, denotes the static dielectric constant. Expression (18) differs from that given in [13] in the additional factor E~/ E , , which is of the order 0.1 for our materials.…”

Deformation potential theory for optical and acoustic phonons in PbSe‐Like semiconductors

“…It should be noted here that the deformation potentials E~I ! and E,, as defined in [ 5 ] differ by a factor vs/coToa from those used here (v, is the sound velocity).…”

“…= E z , as a fitting parameter one obtains a value Ezll lo2 eV; nonpolar interaction appears then st,ronger than polar one. Probably also other inelast,ic scattering mechanisms contribute t o high frequency relaxation time (twooptical-phonon nonpolar scattering [B]) and Eel, is in fact smaller than lo2 eV (for further discussion see [5]). It should be noted here that the deformation potentials E~I !…”

“…0 ) . Then we usually need only the sum of squares of the matrix elements (9) over the phonon polarizations (see [5]). This sum is given by (9) if we replace…”

“…This discrepancy cannot be explained if only one inelastic scattering process (electron-optical-phonon polar interactmion) is assumed [3 to 51. It was suggested i n [5] that a possible additional scattering mechanism is electron-optical-phonon nonpolar interaction. This interaction is forbidden in the L-point, where valence and conduction bands have their extrema, but is allowed beyond L-point since the bands are nonparabolic and their Bloch functions are the mixtures of s-like and p-like functions.…”