Energy levels of A and B excitons in wurtzite‐type semiconductors with account of electron–hole exchange interaction effects

Abstract

The effect of both the complexity of the two upper valence bands as well as the electron-hole exchange interaction on the exciton binding energies in wurtzite-type semiconductors is studied. The energy level scheme and explicit expressions for the lowest exciton states of both A and B series are given. Using recent very accurate experimental data on exciton energies in CdS, the averaged B band hole mass is estimated to 1.6m0, and the position of the n = 1 B(r,) exciton level to about 0.2 meV below the transverse B(r,) level. The longitudinal-transverse splitting of r5 excitons is calculated from a microscopic approach in excellent agreement with experimental data taking into account an interband momentum matrix element P& = 21 eV screened by a background dielectric constant E' = 8. The exchange parameters introduced by Cho are determined for CdS to 3j0 N 1 meV and 9j, = 2.1 meV.Es wird der EinfluS sowohl der komplexen Bandstruktur der beiden oberen Valenzbander als auch der Elektron-Loch-Austauschwechselwirkung auf die Exzitonenbindungsenergie in Wurtzit-Halbleitern untersucht. Das Energieniveauschema und explizite Ausdriicke fur die Grundzustande der A-und B-Exzitonen werden angegeben. Unter Verwendung von neueren sehr genauen experimentellen Werten der Exzitonenenergie in CdS werden die gemittelte B-Band-Lochmasse zu 1,6m0 und die Lage des n = 1 B(r?)-Exzitonenniveaus zu 0,2 meV unter dem transversalen B(I',)-Niveau bestimmt. Die Longitudinal-Transversal-Aufspaltung der r,-Exzitonen wird im Rahmsn einer mikroskopischen Theorie in sehr guter ubereinstimmung mit experimentellen Werten bestimmt, wobei das Interband-Impuls-Matrixelement P& = 21 eV mit einer ,,background"-Dielektrizitatskonstante E' = 8 abgeschirmt wird. Die von Cho eingefiihrten Austauschparameter ergeben sich fur CdS zu 3j0 = 1 meV und 9j, = 2,l meV. l) Now a t : Sektion Wissenschaftstheorie und -organisation der Humboldt-Universitat zu Berlin, Bereich Wissenschaftsgeschichte.

Valence-band ordering and magneto-optic exciton fine structure in ZnO

“…It contains both short-range and long-range contributions [37][38][39] or, as some authors prefer, analytic and nonanalytic terms. [40][41][42] The shortrange part can be written in the form The effect of the long-range terms can be incorporated by replacing J SR by an effective J K , which depends on the wave vector of the exciton translation motion and is different for longitudinal excitons, i.e., Kʈ with the dipole moment of the exciton and transverse excitons. Following Skettrup and Balslev, 39 we can write…”

Band parameters of CdS and CdSe single crystals determined from optical exciton spectra

“…the averaged electron mass rn, = 0.192m0 can be calculated [5], which is some per cent lower than the value given in 131. This is mainly due to the fact that we used here the lower value for the dielectric constant.…”

Magneto‐Reflectance of the B‐Exciton of CdS

“…The evaluated values are A,, = (0.1 5 0.05) meV and A,, = (0.15 0.05) meV. They are half of theoretically estimated exchange interaction energies [31], but twice of experimental data given by Ivchenko et al [29]. These experimental values are quite questionable, because they are deduced from zero-field reflectance spectra for oblique incidence of light, which can be fitted quite well without any exchange interaction energy [ll].…”

“…Furthermore an increase of the radius corresponds to a decrease of oscillator strength [I], which is in contrast to the experiments. Finally a surface layer spike does not appear in reflectivity spectra for an angle of incidence equal to the Brewster angle [lo] interaction energies [31], but twice of experimental data given by Ivchenko et al [29]. These experimental values are quite questionable, because they are deduced from zero-field reflectance spectra for oblique incidence of light, which can be fitted quite well without any exchange interaction energy [ll].…”