AbstractFor p -Bi_2Te_3 crystals grown by the Czochralski method, the temperature dependences of the conductivity, Hall coefficient, thermoelectric power (α), and transverse Nernst–Ettingshausen coefficient are obtained experimentally in the temperature range 77–450 K. The transmittance spectrum in the range 400–5250 cm^–1 is recorded at room temperature. It is shown that, to interpret the temperature dependences of the scattering parameter r and the ratio of the thermoelectric power to temperature (α/ T ), it is essential to take into account the complex valence-band structure and the contribution of heavy holes to transport phenomena. Estimations of the energy band parameters in the context of the two-band model give a hole effective mass close to the free electron mass and the energy gap between nonequivalent extrema at a level of several hundredths of eV. In the absorption spectrum derived from the transmittance spectrum, a sharp increase in absorption defined by indirect interband transitions with the band gap E _ g ≈ 0.14 eV is observed in the region of frequencies ν ≥ 1000 cm^–1. The absorption spectrum calculated from the reflectance data using the Kramers–Kronig relations is in agreement with the experimental absorption spectrum.
For p-Bi2Te3 crystals grown by the Czochralski method, the temperature dependences of the conductivity, Hall coefficient, thermoelectric power (α), and transverse Nernst–Ettingshausen coefficient are obtained experimentally in the temperature range 77–450 K. The transmittance spectrum in the range 400–5250 cm–1 is recorded at room temperature. It is shown that, to interpret the temperature dependences of the scattering parameter r and the ratio of the thermoelectric power to temperature (α/T), it is essential to take into account the complex valence-band structure and the contribution of heavy holes to transport phenomena. Estimations of the energy band parameters in the context of the two-band model give a hole effective mass close to the free electron mass and the energy gap between nonequivalent extrema at a level of several hundredths of eV. In the absorption spectrum derived from the transmittance spectrum, a sharp increase in absorption defined by indirect interband transitions with the band gap Eg ≈ 0.14 eV is observed in the region of frequencies ν ≥ 1000 cm–1. The absorption spectrum calculated from the reflectance data using the Kramers–Kronig relations is in agreement with the experimental absorption spectrum.
The temperature dependence of the Hall coefficient of a single crystal of the p -Sb 2 Te 2.9 Se 0.1 solid solution grown by the Czochralski technique is studied in the temperature range 77–450 K. The data on the Hall coefficient of the p -Sb 2 Te 2.9 Se 0.1 are analyzed in combination with the data on the Seebeck and Nernst–Ettingshausen effects and the electrical conductivity with allowance for interband scattering. From an analysis of the temperature dependences of the four kinetic coefficients, it follows that, at T < 200 K, the experimental data are qualitatively and quantitatively described in terms of the one-band model. At higher temperatures, a complex structure of the valence band and the participation of the second-kind additional carriers (heavy holes) in the kinetic phenomena should be taken into account. It is shown that the calculations of the temperature dependences of the Seebeck and Hall coefficients performed in the two-band model agree with the experimental data with inclusion of the interband scattering when using the following parameters: effective masses of the density of states of light holes m d 1 * ≈ 0.5 m 0 ( m 0 is the free electron mass) and heavy holes m d 2 * ≈ 1.4 m 0 , the energy gap between the main and the additional extremes of the valence band Δ E v ≈ 0.14 eV that is weakly dependent on temperature.
На монокристалле твeрдого раствора p-Sb2Te2.9Se0.1, выращенном методом Чохральского, исследована температурная зависимость коэффициента Холла в диапазоне температур 77-450 K. Полученные по коэффициенту Холла монокристалла Sb2Te2.9Se0.1 в совокупности с данными по эффектам Зеебека, Нернста-Эттингсгаузена и электропроводности проанализированы с учeтом межзонного рассеяния. Из анализа температурных зависимостей четырeх кинетических коэффициентов следует, что при T≤sssim200 K экспериментальные данные качественно и количественно описываются в рамках однозонной модели. При более высоких температурах необходимо учитывать сложное строение валентной зоны и участие в явлениях переноса дополнительных носителей второго сорта (тяжeлых дырок). Показано, что расчeты в двухзонной модели температурных зависимостей коэффициентов Зеебека и Холла согласуются с экспериментальными данными при учeте межзонного рассеяния с использованием следующих параметров: эффективные массы плотности состояний лeгких дырок m*d1~0.5m0 (m0 --- масса свободного электрона) и тяжeлых дырок m*d2~1.4m0, энергетический зазор между основным и дополнительным экстремумами валентной зоны Delta Ev~0.14 eV, слабо зависящий от температуры.
