Midgap traps related to compensation processes in CdTe alloys

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Castaldini, A.
Cavallini, A.
Fraboni, B.
Piqueras de Noriega, Javier
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American Physical Society
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We study, by cathodoluminescence and junction spectroscopy methods, the deep traps located near midgap in semiconducting and semi-insulating II-VI compounds, namely, undoped CdTe, CdTe:Cl, and Cd0.8Zn0.2Te. In order to understand the role such deep levels play in the control of the electrical properties of the material, it appears necessary to determine their character, donor, or acceptor, in addition to their activation energy and capture cross section. Photoinduced-current transient spectroscopy and photo deep-level transient spectroscopy are used to investigate the semi-insulating (SI) samples, and a comparison of the complementary results obtained allows us to identify an acceptor trap, labeled H, and an electron trap, labeled E. Level H is common to all investigated compounds, while E is present only in CdTe:Cl samples. This provides clear experimental evidence of the presence of a deep trap in CdTe:Cl, which could be a good candidate for the deep donor level needed to explain the compensation process of SI CdTe:Cl.
© 1997 The American Physical Society. This research was partially supported by the Cooperation Programme ‘‘Azione Integrata’’ between Italy and Spain and by DGICYT (Project No. PB 93-1256). The authors are indebted to Japan Energy Corporation for the undoped and Cl-doped samples.
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