14 research outputs found
Hall-effect and resistivity measurements in CdTe and ZnTe at high pressure: Electronic structure of impurities in the zincblende phase and the semi-metallic or metallic character of the high-pressure phases
We carried out high-pressure resistivity and Hall-effect measurements in
single crystals of CdTe and ZnTe up to 12 GPa. Slight changes of transport
parameters in the zincblende phase of CdTe are consitent with the shallow
character of donor impurities. Drastic changes in all the transport parameters
of CdTe were found around 4 GPa, i.e. close to the onset of the cinnabar to
rock-salt transition. In particular, the carrier concentration increases by
more than five orders of magnitude. Additionally, an abrupt decrease of the
resistivity was detected around 10 GPa. These results are discussed in
comparison with optical, thermoelectric, and x-ray diffraction experiments. The
metallic character of the Cmcm phase of CdTe is confirmed and a semi-metallic
character is determined for the rock-salt phase. In zincblende ZnTe, the
increase of the hole concentration by more than two orders of magnitude is
proposed to be due to a deep-to-shallow transformation of the acceptor levels.
Between 9 and 11 GPa, transport parameters are consistent with the
semiconducting character of cinnabar ZnTe. A two orders of magnitude decrease
of the resistivity and a carrier-type inversion occurs at 11 GPa, in agreement
with the onset of the transition to the Cmcm phase of ZnTe. A metallic
character for this phase is deduced.Comment: 20 pages, 4 figure