The Hall coefficient
RH and the magneto-resistance
Δρ⁄ρ
0 were measured near 4.2 K on HgTe single crystals annealed at 553-723 K in the Hg vapour of 300 Pa-500 kPa.
RH and
Δρ⁄ρ
0 showed the dependence upon the magnetic field in the range between 0 and 960 kA/m. Analyzing these results by the two carrier model, the carrier concentrations,
Ne and
Nh, and the carrier mobilities, μ
e and μ
h, were obtained. The subscripts e and h refer to electron and hole, respectively.
Ne was in proportion to Hg vapour pressure
PHg, while
Nh was in reverse proportion to that in the experimental range of
PHg. μ
e and μ
h had the maximum μ
e∗ and μ
h∗ at almost the same
PHg∗, respectively. Both varied in proportion to
PHg1⁄2 in the case of
PHg<
PHg∗, but to
PHg−1⁄2 in the reverse case. The concentration product
Ne·
Nh was calculated at different temperatures and found to be constant independent of temperature, even though the crystals were annealed at different temperatures and pressures. The value of
Ne·
Nh⁄
T3 was plotted against 1⁄
T, and then thermal energy gap
Eg=−0.32 meV was obtained from the slope of the curve. The negative value suggested that HgTe behaved as semimetallic.
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