Magnetotunneling spectroscopy is used as a noninvasive and nondestructive probe to produce two-dimensional spatial images of the probability density of an electron confined in a self-assembled semiconductor quantum dot. The technique exploits the effect of the classical Lorentz force on the motion of a tunneling electron and can be regarded as the momentum (k) space analog of scanning tunneling microscopy imaging. The images reveal the elliptical symmetry of the ground state and the characteristic lobes of the higher energy states.

We report large amplitude quantum oscillations and negative differential conductance in the bias voltagedependent photocurrent of p-in GaAs diodes with an AlAs barrier in the intrinsic (i) region. The oscillations appear only when the devices are illuminated with above-band gap radiation. They are strongly suppressed by a weak (ß2 T) in-plane magnetic field. Their period, amplitude, and magnetic field dependence are explained in terms of the quantized motion of confined photoexcited electrons and holes in the triangular potential wells formed by the AlAs barrier and the strong electric field in the intrinsic region. With increasing electric field, the energy levels of the electrons (holes) successively reach the top of their confining potentials, thus leading to a larger overlap of their wave functions with the free carriers in the p-(and n-) doped electrodes and to the observed oscillatory modulation of the recombination rate and photocurrent as a function of the applied voltage. The effect on the photocurrent oscillations amplitude of placing a layer of InAs quantum dots in the AlAs barrier layer is also examined.

Hexagonal boron nitride is a large band gap layered crystal, frequently incorporated in van der Waals heterostructures as an insulating or tunnel barrier. Localised states with energies within its band gap can emit visible light, relevant to applications in nanophotonics and quantum information processing. However, they also give rise to conducting channels, which can induce electrical breakdown when a large voltage is applied. Here we use gated tunnel transistors to study resonant electron tunnelling through the localised states in few atomiclayer boron nitride barriers sandwiched between two monolayer graphene electrodes. The measurements are used to determine the energy, linewidth, tunnelling transmission probability, and depth within the barrier of more than 50 distinct localised states. A three-step process of electron percolation through two spatially separated localised states is also investigated.

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We use magnetotunnelling spectroscopy as a non-invasive probe to produce two-dimensional spatial images of the probability density of an electron confined in a self-assembled semiconductor quantum dot. The images reveal clearly the elliptical symmetry of the ground state and the characteristic lobes of the higher energy states.