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resonance spectroscopy and interband magneto-absorption are applied to the investigation of the Hgl-,Cd,Te alloys system in the range of composition x < 0.3. Magnetotransmission measurements are performed a t 4.2 K up to 60 kG in both the spectral regions (hw < 16 meV and hw > 120 meV), on identical unoriented samples, in the Faraday and Voigt geometries. Magnetooptical data are analyzed using the virtual crystal approximation. All interband and intraband magnetooptical transitions are interpreted in terms of Fa and rs Landau levels described by the Pidgeon and Brown model. The Kane matrix element, the interaction gap, and the Luttinger parameters are determined for each alloy composition from the comparison between theory and experiments. Magnetooptics also provide information on the evolution of the resonant acceptor states with the composition. Des experiences de resonance dans le domaine submillimetrique et do magnetoabsorption interbande ont 6t6 appliquees h l'etude du systeme dalliages Hgl-,Cd,Te, dans la gamme de composition x < 0,3. Des mesures de magnetotransmission ont BtB effectuees h 4,2 K, jusqu'h 60 kG, dans lea deux regions spectrales (hw < 16 meV e t fiw > 120 meV) sup des Bchant,illons identiques, non orient&, en operant dans les configurations Voigt et Faraday. Les donnees magnetooptiques obtenues ont kt6 analysees dans I'approximation du cristal virtuel. Toutes les transitions magnetooptiques interbandes et intrabandes ont 6th interprktkes en utilisant la description des niveaux de Landau des bandes Fa et Fa, obtenue par le modBle de Pidgeon et Brown. L'BlBment de matrice de Kane, le gap d'interaction et les parametres Luttinger ont At6 determines pour chaque alliage h partir de l'analyse theorique des donnees exphimentales. Les donnees magnetooptiques ont, de plus, permis d'ktudier l'evolution des accepteurs rksonnants avec la composition.

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Magnetoabsorption associated with I 6 I, transitions was investigated at 4.4 K, on pure n-type HgTe thin crystals in the spectral region 300-400 meV for a and m polarizations. Analysis of experimental spectra is performed using both the three-band model (including the nonparabolicity), and the theory of Luttinger. Band parameters are determined by fitting transition energies:Er, -Er, = 302.5 meV, mr /mo =0028+0.00» and gr, = -41+4 at I I 8 Luttinger parameters (y, = -12.8, & =-8. 4, z =-10. 5) satisfactorily explain interband and intraband I'8 magnetoabsorption.The structure of I', magnetic levels near I is quantitatively described by calculating the kH dependence of the energies in the t111] direction. A complex structure is found for a set of heavy holes.