INFLUENCE OF BALLISTIC ELECTRONS ON THE DEVICE CHARACTERISTICS OF VERTICALLY INTEGRATED RESONANT TUNNELING DIODES

We present a systematic study of the ballistic electron contribution to the current-voltage (I-V) characteristics of vertically integrated resonant tunneling diodes (RTDs) separated by doped spacer layers (W(sp)). A magnetic field (B) transverse to the tunneling direction was used to tune the electron's longitudinal energy. The results confirm the isolated circuit element picture of the W(sp) = 1000 angstrom sample and the strongly coupled description of the 0 angstrom sample. This work shows that even for some nominally isolated RTDs (in this work for W(sp) = 400 and 500 angstrom), the I-V characteristics can undergo striking B-induced changes. This effect is due to resonant charge buildup in the well of the collector RTD from the relatively weak ballistic component of the current traversing the doped spacer region. A simple model that includes a calculation of the conduction-band profile and quantum well energy levels under bias gives good agreement with the data.