Tunneling through narrow-gap semiconductor barriers

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Abstract
Tunneling probability calculations through the gap of narrow‐gap semiconductors reveal that a large increase in current density near zero bias can be expected when electrons tunnel near the top of the valence band, or conversely holes near the bottom of the conduction band. This effect is obtained by extending the nonparabolic relativistic dispersion relation into the gap to describe the imaginary electron wave vector k which is used in the Wentzel–Kramers–Brillouin calculation. The effect is not limited to that case because it is due to the fact that at the band edges the wave vector goes to zero, or to a Brillouin zone edge k0 value. A double heterojunction device is proposed in Pb1−zSnzTe to illustrate this property, and the tunneling current through it fully modeled. Under a bias voltage applied to the semiconductor, electrons are forced away from the valence‐band edge. The tunneling probability is then decreased, because k is larger and a negative resistance is expected.