Transportuntersuchungen an resonanten Tunneldioden mit Abmessungen im Sub-Mikrometerbereich

To investigate the transport properties of resonant tunneling diodes in the single electron regime two series of diodes with dimensions in the sub-micron range have been processed on the base of MBE-grown AlGaAs/GaAs/ AlGaAs double barrier heterostructures. For this purpose two different technologies have been developed: The diodes of a first series have been structured by dry chemical etching as mesa devices with a surrounding Schottky-gate. A second series of diodes has been structured with a completely planar technology by an ion implantation process. Transport measurements at different temperatures down to 50 mK reveal clearly resolved current steps due to single electron tunneling for both types of diodes. In the case of the mesa-structures tunneling through defect states can be ruled out as a reason for these current steps. Moreover we could show that the current steps are exclusively due to quantisation effects of the gate potential. Magneto-transport measurements of the mesa-structured diodes at a temperature of 50 mK show an oszillatory dependence of the onset voltages of the current steps on a magneticfield applied parallel to the direction of transport. At high magnetic fields a saturation like behaviour occurs. Both effects can be explained by boundary conditions for the electron number and the Fermi-level in the electron supply layer next to the double barrier structure