Enhanced electrical transparency by ultrathin LaAlO₃ insertion at oxide metal/semiconductor heterointerfaces

We demonstrate that the electrical conductivity of metal/semiconductor oxide heterojunctions can be increased over 7 orders of magnitude by inserting an ultrathin layer of LaAlO₃. This counterintuitive result, that an interfacial barrier can be driven transparent by inserting a wide-gap insulator, arises from the large internal electric field between the two polar LaAlO₃ surfaces. This field modifies the effective band offset in the device, highlighting the ability to design the electrostatic boundary conditions with atomic precision.