Impurities and intervalence band magneto‐optical transitions in tellurium

Abstract

Recent magneto‐optical results obtained in the energy range 100 to 170 meV, for ϵ ‖ c and H ⊥ c, are reported and analysed. Transitions of holes from acceptor states and transitions of holes from the first Landau level of the M band to the quantum levels of the M′1 band are identified by investigating the temperature dependence of the magnetoabsorption lines between 2 and 10°K. Calculations of the energies and intensities of the intervalence band magneto‐optical transitions are performed. The comparison of theoretical and experimental data enables one to determine the parameters of the valence band. The fine structure of magnetoabsorption spectra investigated by wavelength modulation technique indicates the existence of several impurity states. The binding energy of the acceptor ground state is estimated to be about 1.4 meV.

Magnetooptical investigation of the conduction band in tellurium

“…The transverse hole effective mass at kz ~ 0, mvtlmo = 0.118 ± 0.003 determined from our interband magnetooptical data is higher than the value 0.108 obtained from cyclotron resonance experiments [12] at the top of the valence band, while the dispersion relation eq. (7) (with q 0) [12,19] predicts the opposite variation with k,-of the transverse effective mass. We verified that our magnetoabsorption spectra cannot be properly fitted with m,,,Imo , 0.108.…”

“…These particularities can be explained from the theoretical description of the transition energies, (eq. (18), (19)). Transitions n' -+ n+ and n' .... nare expected to present a specific behaviour in the magnetic field resulting from the different localization of the critical point at kz = SY±/2(Aa).…”

“…The field dependence of transition energies (eq. (18), (19)) is rather complicated and depends crucially on the values of the parameters via X t or Y,,. After testing several possibilities we selected the region for the parameters in which the field dependence of transition energies is nearly linear with two different regions of convergence of all the lines extrapolated to zero field.…”

“…(16) corresponding to Ynare slowly varying with the magnetic field and n. Thus the energies En,n(H) given by eq. (19) will have an almost linear variation, and the extrapolation at zero field leads to i.e. below the energy gap.…”

Photoconductivity of tellurium by CO2 laser

“…the mobility ratio ,u2/,u1 must be known. For ,u2 we have ,u211 = (e/m2,1)(tf)), where m2 11 is the light hole mass from the magnetoabsorption data [20]. I n the framework of our model pulse relaxation of light holes (t$) is governed by the strong interband scattering H, + H4 rather than by intraband relaxation (H, -H5) assisted by acoustic phonans: l /~z -,~ > 1/zE.…”