High magnetic field studies of tunnelling through X-valley-related silicon donor states in GaAs/AlAs heterostructures

Four resonances have been observed in the current-voltage characteristics of a GaAs/AlAs single-barrier diode incorporating a delta-layer of silicon donors in the barrier. High magnetic fields applied perpendicular to the plane of the barrier are used to examine the nature of the resonant features in the current-voltage characteristics of the diode, The diode has been modelled, showing that the voltage positions and magnetic field dependence of the lower bias resonances are consistent with tunnelling through strain-field split ground stales of silicon impurities below the X-conduction band minima of AlAs.