Optical investigations of defects inCd1−xZn

Investigation of the origin of deep levels in CdTe doped with Bi

“…The fitting of this broad emission was done using the HuangRhys equation 27 and defining two bands: the A band formed by a complex between V Cd and shallow donors and the Y band which arises from the exciton recombination in defects such as dislocations. 28,29 Very good agreement between the experimental and theoretical values is obtained and the parameters extracted from the fitting procedure, 27 including the Huang-Rhys parameter ͑S͒, the energy of the zero phonon line ͑E Z0 ͒, the phonon energy ͑E Ph ͒, and the ionization energy of the donor involved in the A band, are presented in Table III.…”

Midgap traps related to compensation processes in CdTe alloys

“…This suggests that level E could be considered the deep donor needed to explain fully the compensation process in CdTe:Cl. 3,5,6,17,19 It is worth noting that E cannot be due to the thermal emission of electrons from the recombination center H both because level E is detected only in CdTe:Cl samples, and because the thermal activation energy of level H for electron emission has been calculated to be lower than that for hole emission, 15 while, in our case, E has a greater activation energy than H. The role played by the levels detected in this work is different for each investigated II-VI compound. In Cd 0.8 Zn 0.2 Te, which is intrinsically semi-insulating, level H is the only deep trap located near the Fermi level at midgap and it possibly contributes to the pinning of the Fermi level.…”

“…The resulting complex (V Cd -Don Te ) is the so-called center A, 1 which acts as a single acceptor located at E V ϩ0.15 eV. [2][3][4] Its energy level is too shallow to account for the pinning of the Fermi level observed in compensated Si II-VI compounds, and the existence of a deep donor has been suggested to explain the compensation process. 3,5 While the introduction of group-V impurities is known to directly introduce deep levels which play a significant role in the resulting semi-insulating behavior of the material, group-III impurities do not directly generate deep levels but only introduce shallow ones.…”

“…[2][3][4] Its energy level is too shallow to account for the pinning of the Fermi level observed in compensated Si II-VI compounds, and the existence of a deep donor has been suggested to explain the compensation process. 3,5 While the introduction of group-V impurities is known to directly introduce deep levels which play a significant role in the resulting semi-insulating behavior of the material, group-III impurities do not directly generate deep levels but only introduce shallow ones. 6 In order to study the electrical activity of the deep traps, we used electrical spectroscopy methods which can be applied to SI materials, namely, PICTS ͑photoinduced-current transient spectroscopy͒ and PDLTS ͑photo deep-level transient spectroscopy͒.…”

Experimental Verification of Calculated Lattice Relaxations Around Impurities in CdTE

“…Since a site sensitive XAFS detection has not yet been successfully developed for these systems, one has to be sure that the signal from other possible configurations does not obscure the signal from the assumed purely substitutional one. While for As in CdTe, other conflicting configurations might be various cluster configurations, the most likely alternative configurations for Br in CdTe are the well-known A-center [4] or various forms of DX-centers [5].…”