Negative differential conductance in Al/δ-GaAs/AlGaAs tunnel junctions

A mechanism of inherent negative differential conductance (NDC) in tunnelling from a metal into 2D subband in a quantum well is proposed. NDC is a consequence of barrier height increase with bias for electrons tunnelling into 2D subband. The mechanism can bring to NDC in the HEMT-like structures with tunnelling between the gate and 2D channel. An example Al/δ-doped GaAs/AlGaAs structure is proposed and theoretical tunnel characteristics are presented.