Effect of annealing on the electrical properties of polycrystalline intermetallic compound HgTe

Polycrystalline HgTe samples have been prepared by taking Hg and Te in stochiometeric compositions. The effect of annealing in mercury has also been studied. The effect of temperature on the electronic conduction mechanism and grain‐boundary states has been observed through the measurement of Hall coefficient R_H resistivity (ρ) and Hall mobility μ_H=(R_H/ρ) on the polycrystalline HgTe in the temperature range ∼77–350 K. It is found that in electronic conduction in the low‐temperature range, the conduction is dominated by the thermionic emission of electrons over the grain boundaries. At a critical temperature T_c where the barrier height Φ_b and, hence the width of the space‐charge region near the grain boundaries tends to zero, a crossover from the barrier limited to the mobility limited resistivity occurs. R_H is found to be thermally activated over the temperature range where the conduction mechanism is governed by the grain‐boundary barrier. The experimental results are explained on the basis of a grain‐boundary trapping model combined with two‐phase model. It is found that the mobility and the grain size increased with annealing time. We achieved the carrier mobility of polycrystalline HgTe at 270 K to as much as 11 000 cm²/V s.