Contact Resistance of PL173 Quantum Hall Samples Developed in Euromet Project N°346

The authors have measured the physical and metrological parameters of QHE samples developed by BNM-LNE and LEP in Euromet project 346. It appears that the samples marked PL173 have good characteristics, but suffer from a contact resistance that behaves asymmetric with respect to the current polarity. At the point where electrons are injected into the two-dimensional electron gas, the increase in contact resistance occurs at significantly lower currents than for currents in the other direction. Several methods have been tried to improve the behaviour of the contacts, but so far without success