Noise measurements in semiconductor nanodevices
Résumé
We review noise measurements in quantum coherent semiconductor nanodevices. Quantum coherent conductors are characterised by their small size such that a carrier crossing the conductor preserves its phase coherence. This requires no inelastic energy exchange with photon, phonon, plasmons or other dynamical excitations and no phase averaging by random noise. Such highly quantum regime is best obtained at very low temperature. The quantum coherent regime can be realised in metals or in doped semiconductors of sub-micron size. Here, we concentrate on semiconductor nanodevices. Doped semiconductors and in particular 2D electron systems realised at the interface of modulation doped heterojunctions have enabled the realisation of Quantum Point Contacts, a key tool to test the physics of quantum noise.
Shot noise played an important role in the development of new ideas in Condensed Matter. The analogy between the quantum noise of electrons transferred through a conductor and the noise of photons propagating in an optical medium has pushed towards the development of Electron Quantum Optics where quantum point contact was used to mimic optical beam splitters. We will see that quantum shot noise can also be used to measure the (fractional) charge of electronic carriers, to perform the energy spectroscopy of electronic excitations, to determine unambiguously the transmission probability of electronic quantum modes, to count the number of electron and hole generated by AC excitations and even to detect THz radiation.