Preparation of semi‐insulating CdTe doped with group IV elements by post growth annealing

Abstract

Thermodynamic conditions for post-growth annealing to prepare near stoichiometric semi-insulating CdTe are studied for undoped, and Sn and Ge-doped single crystals. The main aim of the annealing procedure was to obtain high resistive material with the minimal concentration of native and foreign defects. The high temperature (200 -1000 °C) in-situ conductivity σ and Hall effect measurements were used to control the native defect density and to determine the Cd pressure p Cd at which shallow defects are compensated. It is shown that contrary to the undoped samples in which the change of the type of conductivity by variations of p Cd is easy, the Sn-and Ge-doped samples exhibit a much more stable behavior due to the Sn (Ge) selfcompensation. It was found that: the temperatures near 500 °C is optimum for the real-time annealing of bulk samples, the chemical diffusion is sufficiently fast at these temperatures while the uncontrolled change of defect density distribution during the subsequent cooling process is minimized. The time-dependent charge measurement technique was used to characterize the room-temperature specific resistivity distribution in the as-grown crystals, which indirectly controls the dynamic of solidification process. This allows us to consider the specific resistivity distribution along the growth direction of each crystal in terms of superposition of segregation and self-compensation phenomena.

Magnetization dependence on electron density in epitaxial ZnO thin films codoped with Mn and Sn

“…Limited results on the doping behavior of Sn in ZnO indicate that it introduces a donor state, [45][46][47][48][49] although in some II-VI compound semiconductors, Sn is an amphoteric dopant, substituting on either the II or VI site. 50,51 For ZnO, the expectation is that Sn will substitute on the Zn site due to a close match in ionic radii between Zn +2 ͑0.074 nm͒ and Sn +4 ͑0.069 nm͒. For the epitaxial films considered in this work, Sn behaves as a donor.…”

Charge carrier and spin doping in ZnO thin films

“…This carrier density is substantially lower than that seen for undoped epitaxial films, and is consistent with the reduction of shallow donors. Limited results on the doping behavior of Sn in ZnO indicate that it introduces a donor state [73 -77], although in some II -VI compound semiconductors, Sn is an amphoteric dopant, substituting on either the II or VI site [78,79]. For ZnO, the expectation is that Sn will substitute on the Zn site due to a close match in ionic radii between Zn 2+ (0.074 nm) and Sn 4+ (0.069 nm).…”

Point defects and diffusion in cadmium telluride

“…The forms for the calculations of various defect and complex densities within quasichemical formalism can be found e.g. in Turkevych et al [24].…”