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In order to improve the photoconversion efficiency, we consider the possibility of increasing the photocurrent in solar cells exploiting the electron photoemission from small metal nanoparticles into a semiconductor. The effect is caused by the absorption of photons and generation of local surface plasmons in the nanoparticles with optimized geometry. An electron photoemission from metal into semiconductor occurs if photon energy is larger than Schottky barrier at the metal-semiconductor interface. The photocurrent resulting from the absorption of photons with energy below the bandgap of the semiconductor added to the solar cell photocurrent can extend spectral response range of the device. We study the effect on a model system, which is a Schottky barrier n-GaAs solar cell, with an array of Au nanoparticles positioned at the interface between the semiconductor and the transparent top electrode. Based on the simulations, we chose to study disk-shaped Au nanoparticles with sizes ranging from 25nm to 50nm using electron beam lithography. Optical characterization of the fabricated devices shows the presence of LSP resonance around the wavelength of 1250nm, below the bandgap of GaAs.

We examine the edge states picture as applied to the electron–hole system, and show that compensated quantum Hall states are fundamentally different to quantum Hall states of single carrier type systems. Measurements of their current driven breakdown are described, and we show that these states have very small breakdown currents.

We find that an InAs/GaSb based electron–hole system exhibits insulating behaviour when the numbers of occupied electron and hole Landau levels are equal. In this insulating state, the Hall resistance becomes symmetric under field reversal, and both the Hall and longitudinal resistances display reproducible fluctuations. We propose a simple model based on edge states to account for these properties, and show that a comparison to the conductivity measured from a Corbino disc is consistent with the model.