MAGNETO-TUNNELING STUDIES OF CHARGE BUILDUP IN DOUBLE BARRIER DIODES

The accumulation and depletion layers on each side of a Double Barrier Diode (DBD) are believed to have an important influence on DC and high frequency behaviour of such devices. A magnetic field (B) parallel to the growth axis induces Landau quantization in the structure. Very large current oscillations have been observed by sweeping B for fixed biases of the diode in the region before negative differential resistance. Variations of energy levels of the structure relative to the Fermi level in the emitter are deduced from these oscillations. We have observed a very slow variation of the period of oscillations versus total bias in GaAs-(AlGa) As DBD structures with large (50 nm) undoped spacer layers in emitter and collector. To explain this behaviour we propose a mechanism in which resonant tunneling occurs essentially between two localized states.