Charge Buildup, Intrinsic Bistability and Energy Relaxation in Resonant Tunneling Structures: High Pressure and Magnetic Field Studies

Abstract

Hydrostatic pressure and high magnetic fields are used to study space charge buildup under resonant tunneling conditions in an asymmetric double barrier structure based on n-type GaAs/(AlGa)As. The space charge buildup gives rise to an intrinsic bistability effect in the current-voltage characteristics. The pressure-induced increase in Γ-X tunneling and scattering reduces the resonant space charge buildup and allows us to study the transition from intrinsic bistablity to ordinary negative differential conductivity in I(V). Over a certain pressure range a sharp resonance is observed in which electrons tunnel into the well via Γ-states and scatter out mainly via X-states, a clear example of sequential tunneling. The final part of the paper describes a remarkable enhancement of the intrinsic bistability when a quantizing magnetic field is applied perpendicular to the barriers. This is associated with the strong degeneracy of Landau levels at high magnetic fields.