Axially doped p-i-n InAs0.93Sb0.07 nanowire arrays have been grown on Si substrates and fabricated into photodetectors for shortwave infrared detection. The devices exhibit a leakage current density around 2 mA/cm(2) and a 20% cutoff of 2.3 μm at 300 K. This record low leakage current density for InAsSb based devices demonstrates the suitability of nanowires for the integration of III-V semiconductors with silicon technology.

Linear transverse magnetoresistance is commonly observed in many material systems including semimetals, narrow band-gap semiconductors, multi-layer graphene and topological insulators. It can originate in an inhomogeneous conductor from distortions in the current paths induced by macroscopic spatial fluctuations in the carrier mobility and it has been explained using a phenomenological semiclassical random resistor network model. However, the link between the linear magnetoresistance and the microscopic nature of the electron dynamics remains unknown. Here we demonstrate how the linear magnetoresistance arises from the stochastic behaviour of the electronic cycloidal trajectories around low-mobility islands in high-mobility inhomogeneous conductors and that this process is only weakly affected by the applied electric field strength. Also, we establish a quantitative link between the island morphology and the strength of linear magnetoresistance of relevance for future applications.

The replacement of SiO2 gate dielectrics with metal oxides of higher dielectric constant has led to the investigation of a wide range of materials with superior properties compared with SiO2. Despite their attractive properties, these high-k dielectrics are usually manufactured using costly vacuum-based techniques. To overcome this bottleneck, research has focused on the development of alternative deposition methods based on solution-processable metal oxides. Here we report the application of spray pyrolysis for the deposition and investigation of Al2x-1·TixOy dielectrics as a function of the [Ti(4+)]/[Ti(4+)+2·Al(3+)] ratio and their implementation in thin film transistors (TFTs) employing spray-coated ZnO as the active semiconducting channels. The films are studied by UV-visible absorption spectroscopy, spectroscopic ellipsometry, impedance spectroscopy, atomic force microscopy, X-ray diffraction and field-effect measurements. Analyses reveal amorphous Al2x-1·TixOy dielectrics that exhibit a wide band gap (∼4.5 eV), low roughness (∼0.9 nm), high dielectric constant (k ∼ 13), Schottky pinning factor S of ∼0.44 and very low leakage currents (<5 nA/cm(2)). TFTs employing stoichiometric Al2O3·TiO2 gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with low operating voltages (∼10 V), negligible hysteresis, high on/off current modulation ratio of ∼10(6), subthreshold swing (SS) of ∼550 mV/dec and electron mobility of ∼10 cm(2) V(-1) s(-1).

We report cyclotron resonance ͑CR͒, transverse magnetoresistance ͑MR͒, and Hall effect studies of a series of n-type InAs 1−x N x epilayers grown on GaAs with x up to 1%. The well-resolved CR absorption lines, the classical linear MR, Shubnikov-de Haas magneto-oscillations, and negative MR revealed in our experiments provide a means of probing the effect of the N atoms on the electronic properties of this alloy system and reveal qualitative differences compared to the case of the wider gap III-N-V compounds, such as GaAs 1−x N x . In GaAs 1−x N x electron localization by N levels that are resonant with the extended band states of the host crystal act to degrade the electrical conductivity at small x ͑ϳ0.1%͒. These phenomena are significantly weaker in InAs 1−x N x due to the smaller energy gap and higher energy of the N levels relative to the conduction band minimum. In InAs 1−x N x the electrical conductivity retains the characteristic features of transport through extended states, with electron coherence lengths ͑l ϳ 100 nm at 2 K͒ and electron mobilities ͑ =6 ϫ 10 3 cm 2 V −1 s −1 at 300 K͒ that remain relatively large even at x =1%.

GaAs-based solar cells containing stacked layers of nanostructured type II GaSb quantum ring solar cells are reported which show significantly enhanced infrared photo-response extending out to 1400 nm. The ring formation reduces the net strain energy associated with the large lattice mismatch making it possible to stack multi-layers without the need for strain balancing. The (1 sun) short-circuit current for a 10 layer sample is enhanced by ∼6% compared to a GaAs control cell. The corresponding open-circuit voltage of 0.6 V is close to the theoretical maximum expected from such structures.

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Powerful (light emitting diodes) LEDs which exhibit more than 3.5 mW of output power at room temperature have been fabricated by liquid phase epitaxy (LPE) and characterized. These LEDs are well matched to the CH4 absorption spectrum and confirm the potential of the devices as a key component for use in an infrared CH4 gas sensor. We report on the efficient interface electroluminescence in our LEDs across the InAs/InAsSbP heterojunction consistent with type II emission. This directly suppresses the Auger recombination and enables these sources to emit maximum powers in excess of 3 mW at room temperature. Furthermore, the use of Yb rare earth ion gettering in these devices was found to be effective in increasing the LED output power. We attribute this to a reduction in the residual carrier concentration arising from the removal of unintentional donors and point defects in the InAs active region material. The ring contact geometry was also found to be superior when compared to the dot contacts in our structures. The LEDs demonstrated in this work are sufficiently powerful to be used in a practical methane gas sensor.

Nitrogen incorporation in InAsN epilayers grown by radio-frequency plasma-assisted molecular beam epitaxy was investigated as a function of growth conditions. Reduced growth rate, growth temperature, and arsenic flux significantly enhance the nitrogen incorporation. Optimal growth conditions allowed us to obtain high quality InAsN with nitrogen composition of up to 2.5%. The epilayers exhibit intense 4K photoluminescence (PL) with double-peak features, which were attributed to free carrier recombination and localized carrier recombination. Strong room temperature PL emission up to a wavelength of 4.5μm is obtained.