High mobility in a two dimensional electron system with a thinned barrier

A variety of novel experiments involving mesa structures of a two dimensional electron system (2DES) require the fabrication of a metal electrode on top of the mesa. We describe a fabrication process in which the top barrier layer is thinned to achieve low interface resistance, and the effect of the diminished barrier layer on the transport characteristics of carriers in the 2DES is studied. The sample is an InAs inserted heterostructure with strong intrinsic spin–orbit interaction α . Shubnikov–de Haas, resistivity and Hall experiments are used to characterize the carrier density, mobility and spin–orbit interaction of the carriers and to compare characteristics with a sample in which the structure is not altered. Our results show that the integrity of the heterostructure and the characteristics of the carriers can be maintained when the thickness of the top barrier is as little as 5 ± 2 nm.