Tunnelling in Pb-p-HgCdTe Schottky barriers in longitudinal and transverse magnetic fields

Abstract

The tunnelling current in reverse-biased Pb-p-Hg,-,Cd;Te (x = 0.2-0.3) Schottky barriers is investigated in a magnetic fieid H = 0-50 kOe parallel and perpendicular to the electric field E in the temperature range T = 20-250 K. The tunnelling current in magnetic fields of both orientations decreases by a factor of 10 and more. For H 11 E the magnitude of the effects as well as the dependence of the interband tunnelling current on magnetic fieid, reverse voltage (electric field), temperature and alloy composition is in good agreement with the theory. In contrast to the existing theory, for H I E orientation the magnetic-feid dependence is similar to t h e H 11 E case. No peculiarities are observed near the critical magnetic field H,, = cE/s (s is the Kane velocity). The experimental results for H I E may be explained qualitatively if we take into account a non-resonant scattering of light holes during tunnelling through the barrier. The scattering length estimated from the ratio of the effects in two orientations is proportional to H-'" and is of the order of the magnetic length. as would be exDected for quantum diffusion in crossed fields.

Strong magnetic field effect on over-the-barrier transport in Pb-p-Hg1 −xCdxTe Schottky barriers

“…The interband and trap-assisted tunnelling currents in temperature range from T = 20 K to T = 80 K decrease by a factor 10 and more. The dependence (9) agrees well with the magnetic fields dependence of the tunnelling currents investigated in similar Pb-p-HgCdTe SB in [7]. The ∆ϕ im values calculated for zero bias and T = 140 K are presented in table 1.…”

“…Due to a small effective mass the light holes dominate in tunnelling current through the SB grown on p-Hg 1−x Cd x Te. As a result, the strong magnetic field effect on tunnelling was observed in these structures [4].…”

“…In both cases the light holes carry over a current. It should be noted that the discussed effect of insulator layer on thermionic current does not concern the results of works [6,7] concidering the tunnelling and magneto-tunnelling in SB on p− HgCdTe at low temperatures T < T 0 . The influence of this layer on the tunnelling currents is negligibly small because its tunnelling transparency for light holes P lh ∼ 0.2 − 0.4 many orders over exceeds the transparency of depletion layer P SB ∼ exp(−λ 0 ) where λ 0 = 5 − 30 [7].…”

“…The influence of a magnetic field on the transport in Schottky barriers was investigated in work [7] at low temperatures, when the tunnel currents dominate. However we have not found any works studying the magnetic field effect on the abovebarrier transport in SB.…”

“…In addition to the overthe-barrier current (dominated carrier transport mechanism in wide-gap semiconductor devices), the barrier structures fabricated on the narrow gap Hg 1−x Cd x Te semiconductor exhibit significant contribution of tunnelling currents, which limit diode performance. The mechanisms of tunnelling in Pb-p-Hg 1−x Cd x Te SB were studied in our previous works [3,4]. Due to a small effective mass the light holes dominate in tunnelling current through the SB grown on p-Hg 1−x Cd x Te.…”