Transport property of zero-gap semiconductors under tensile stress

The band structure of symmetry-induced zero-gap semiconductors under uniaxial tensile stress is studied. It is found that there exist regions in the reciprocal space where one component of the effective-mass tensor of either electrons or holes becomes negative. In particular, the anomalous region for holes can be made sufficiently large to allow for the occurrence of negative-differential-resistance (NDR) effect. The $I-V$ characteristics for $p$-type $\alpha -\mathrm{S}\mathrm{n}$ and HgTe at both zero temperature and finite temperature (4.2 and 77°K) are obtained by simple transport calculations. From these calculated $I-V$ characteristics, one gets some idea about the sample requirements and magnitude of stress needed for NDR effect.