Optical identification of substitutional acceptors in refined ZnTe

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147

The photoluminescence spectroscopy of undoped CdTe crystals provides information on two acceptors which are the main contaminants of as-grown crystals. These acceptors called y and z have their respective ionization energies a t 147 and 108 meV. A complete series o f two hole replicas iu observed for y and only one for z. These acceptors are believed to be due to Cu and A@; impurities. Backdoping experiments with Li and Na give rise to new transitions. From the conduction bandacceptor level transitions, t,he ionization energies are respectively obtained to 57.8 and 58.8 meV. In the case of Li, some extra-lines are tentatively identified as phonon interacting two-hole transitions.La spectroscopie de la photoluminescence de CdTe non dope fournit des informations sur deus nccepteurs qui sont des contaminants du matkriau brut de croissance. Ces accepteurs, appeIBs y et z ont leurs Bnergies d'ionisation respectivement A 147 et 108 meV. Une serie complBte de repliques a deux trous a 6th observee pour y et seulement une replique pour z. Ces accepteurs sont probablement dus aux impuretks Cu et Ag. Des experiences de dopage avec Li et Na donnent naissance a de noovelles transitions. A partir des recombinaisons bande de conduction-niveau accept.eiir, les dnergies d'ionisation ont kt6 respectivernent obtenues 5'7,s e t 58,5 meV. Dam le cas du Li, des ruies supplhmentaires sont attribuees it une transition ? i , deux trous, perturbke par une interaction avec des phonons.

Section: Diffusionsupporting

confidence: 78%

Shallow Acceptors in Cadmium Telluride

Molva

Chamonal

Pautrat

1982

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147

“…However, we find that the T d symmetric ground state with a delocalized effective‐mass like hole wave‐function (PHS) lies 0.3 eV lower in energy than the symmetry‐broken configuration. Thus, the generalized Koopmans formalism correctly predicts the well established effective‐mass behavior of Li Zn in ZnTe, and the calculated Li acceptor ionization energy of 0.08 eV reflects the shallow effective‐mass acceptor level (experiment: 0.06 eV 89). Shallow ground state without barrier (Fig.…”

Section: The Balance Between Localization and Delocalizationmentioning

confidence: 60%

Predicting polaronic defect states by means of generalized Koopmans density functional calculations

Lany

2010

Lattice defects in semiconductors and wide-gap materials which create deep levels in an open-shell electronic configuration can give rise to so-called defect bound small polarons. This type of defects present a challenge for electronic structure methods because the localization of the defect state and the associated energy levels depend sensitively on the ability of the total-energy functional to satisfy the physical condition that the energy E(N) must be a piecewise linear function of the fractional electron number N. For practical applications the requirement of a linear E(N) is re-cast as a generalized Koopmans condition. Since most functionals do not fulfill this condition accurately, we use parameterized perturbations that cancel the non-linearity of E(N) and recover the correct Koopmans behavior. Starting from standard density functionals, we compare two types of parameterized perturbations, i.e., the addition of on-site potentials and the mixing of nonlocal Fock exchange in hybrid-functionals. Surveying a range of acceptor-type defects in II-VI and III-V semiconductors, we present a classification scheme that describes the relation between hole localization and the lattice relaxation of the polaronic state.

“…We have shown that the p-type conductivity of ZnTe originates mainly from CuZn [2] and Lizn [3], and for a smaller part from Agzn [a] rather than from intrinsic defects. The infrared absorption spectra of As, P, and Li acceptors in ZnTe have been published [5].…”

Section: Introductionmentioning

confidence: 99%

Infrared Absorption by Ag, Cu, and Au Acceptors in ZnTe

Samindayar¹,

Magnéa²,

Pautrat³

et al. 1981

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These results are in good made on ZnTe doped with Ag, Cu, and Au acceptor impurities. Observin the framework of the theory of Baldereschi. The binding energies E, 0.5), and (271.6 f 0.5) meV for Ag, Cu, and Au impurity, respectively. agreement with that deduced from luminescence experiments. The average number of emitted phonons is deduced for all known acceptors in ZnTe (Li, P. As, Ag, Cu, and Au) using luminescence and IR measurements. An empirical relation hJ = 62E: is found. The cross-section for Au in ZnTe is found to be (3.5 & 0.7) X 10-la om2 with an effective field ratio which ranges between 2.3 and 4.Des mesures de transmission infrarouge ont 6th effectuhes sur des Bchantillons de ZnTe dopPs avec les accepteurs Ag, Cu et Au. La discussion, B partir de la thBorie de Baldereschi, a permis de dbfinirlesbnergiesd'ionisation E,. Les de d6terminer le nombre moyen de phonons Bmis 5, pour tous les accepteurs connus dans ZnTe (Li, P, As, Ag, Cu, Au), e t la relation empirique = 62EE a pu &re dbduite. Enfin, la section de capture optique de l'accepteur Au dans ZnTe a 6th dkduite des mesures de transmission IR.On a trouv6 u = (3,5 5 0,7) x cm2 avec un coefficient de champ effectif se situant entre 2, 3 et 4.