Investigation of a contacting scheme for self-assembled cleaved edge overgrown InAs nanowires and quantum dot arrays

A contacting scheme to measure the transport properties into self-assembled InAs Quantum Wires (QWRs) or Quantum Dots (QDs) is presented. The nanostructures are formed on the (110) cleaved edge of a AlAs/AlGaAs heterostructure substrate by means of the Cleaved Edge Overgrowth (CEO) technique and Molecular Beam Epitaxy (MBE). The InAs nanostructure grows directly on top of the AlAs layer, which hosts a two dimensional electron gas (2DEG). In a transistorlike schematic of the device, the 2DEG acts as a contact to the InAs nanostructure. A top gate is used to deplete the 2DEG, thereby defining the InAs nanostructure as a channel between source and drain. Measurements confirm that the device can be operated as a field-effect transistor, but no evidence of a current flow through the InAs QWRs can be found. Numerical calculations of the electron density and the device band structure confirm that a depletion zone is present in the AlAs layer close to the cleaved edge and the InAs QWR seems electrically isolated from the AlAs 2DEG leads. Possible solutions could be an additional Schottky gate contact on the CEO side or selective doping inside the CEO barrier.