2-D tunneling structures and increased peak to valley current ratio in double barrier quantum systems under perpendicular electric and magnetic bias

Abstract

Tunneling across an electrically biased double barrier system (with potential V along the z-axis) in a transverse magnetic field B (along the x-axis) is studied. The magnetic field-induced coupling of the transverse momentum (ky) with the z-direction motion of the electron selects the minimum value of ky depending on the incident energy εz below which the wave becomes evanescent in nature and is restricted from participating in the tunneling process. With the increase in B, resonant tunneling across the DBS occurs for an increasing range of resonant energy εzr albeit at a particular transverse momentum kyr for each εzr. Thus, the one-dimensional resonant tunneling feature at the quasi-resonant energy εzr0 for the entire spectrum of ky in absence of the magnetic field changes to a two-dimensional resonance structure in the εy and εz plane with the application of the magnetic field. The lower and upper bound of εzr and the corresponding limits on kyr for resonant tunneling based on B and V is spelt out. A formula for current density based on these observations is developed and the current–voltage relation for the DBS in presence of the transverse magnetic field is studied. With the application of the magnetic field the Peak to Valley current ratio (PVCR) calculated on the basis of tunneling current increases by many folds. The effect of Zeeman splitting due to interaction of spin moment of conduction electrons with magnetic field on the tunnel current is discussed.