Strong magnetic field effect on above-barrier transport in Pb-p-HgCdTe Schottky barriers

TL;DR

This study investigates the influence of magnetic fields on above-barrier transport in Pb-p-HgCdTe Schottky barriers, revealing unexpected effects at relatively low fields and highlighting discrepancies with existing theoretical predictions.

Contribution

It demonstrates a significant magnetic field effect on saturation current at low fields and explores the role of light holes, challenging simple theoretical models.

Findings

Over twofold decrease in saturation current at B=0.5 T

Magnetic field effect depends on the ratio of light hole cyclotron energy to thermal energy

Observed effects exceed predictions of simple thermionic current models

Abstract

Due to large difference in effective masses of light and heavy holes it is usually supposed that the above-barrier current in Schottky barriers on p-type semiconductor is controlled only by the heavy holes. However, in real structures, there is an additional potential barrier caused by a oxide layer at interface. For typical values of thickness and height of a barrier its tunnel transparency for light holes can be higher by three order of magnitude than that for heavy holes. Due to such separative role of insulator layer one can expect that the current is manly a contribution of light holes. To clear up this problem the investigation of transport in a magnetic field is used as a key experiment in this work. The pronounced magnetic field effect for heavy holes in investigated Pb-p-HgCdTe Schottky barriers is expected only at extremely strong magnetic fields B>10 T within the framework of both diode and diffusion mechanism of transport. At the same time experimentally more than twofold decrease in saturation current is observed even at B=0.5 T at any orientation of magnetic field. The studies performed for HgCdTe with different Kane's gap and at different temperatures show that the magnitude of magnetic field effect is uniquely determined by the ratio of light hole cyclotron energy to a thermal energy. However the magnitude of effect exceeds considerably the prediction of the simple theory and the experimental magnetic field dependencies of a saturation current do not follow the simple exponential falling predicted for thermionic current. The reason of this discrepancy remains a mystery.